Trimetyloaminuria (zespół zapachu rybnego)
Diagnostyka i diagnoza

Trimetyloaminuria (TMAU) to rzadkie, autosomalnie recesywne zaburzenie metaboliczne spowodowane mutacjami w genie FMO3, prowadzące do defektu enzymu monooksygenazy flawinowej 3 i nieprawidłowego metabolizmu trimetyloaminy (TMA). Klinicznie objawia się charakterystycznym, nieprzyjemnym zapachem ciała przypominającym gnijące ryby. Diagnostyka opiera się na ocenie stosunku TMA do N-tlenku trimetyloaminy (TMAO) w moczu, gdzie u pacjentów z TMAU współczynnik utleniania TMAO/(TMAO+TMA) x 100% jest < 25%, podczas gdy u zdrowych osób wynosi > 80-92%. Testy diagnostyczne obejmują obciążenie rybą (300 g), choliną lub trimetyloaminą (600 mg u dorosłych) z późniejszą analizą moczu w okresie 2-12 godzin. Metody analityczne stosowane do pomiaru TMA i TMAO to m.in. spektroskopia 1H NMR, chromatografia gazowa oraz spektrometria mas z jonizacją elektrosprejową i MALDI-TOF. Badania genetyczne są zalecane u pacjentów z wydalaniem > 10% TMA w postaci wolnej aminy, choć w ciężkich przypadkach klinicznych ich wartość diagnostyczna może być ograniczona.

  1. Trimetyloaminuria (zespół zapachu rybnego) – Diagnostyka
    1. Podejrzenie kliniczne
    2. Diagnostyka laboratoryjna
    3. Metodyka badania
    4. Badania genetyczne
    5. Diagnostyka różnicowa
    6. Znaczenie kliniczne wczesnej diagnozy
    7. Centra diagnostyczne
    8. Kolejne rozdziały

Trimetyloaminuria (zespół zapachu rybnego) – Diagnostyka

Trimetyloaminuria (TMAU), znana również jako zespół zapachu rybnego, jest rzadkim zaburzeniem metabolicznym charakteryzującym się nieprzyjemnym zapachem ciała przypominającym woń gnijących ryb. Dolegliwość ta wynika z defektu w produkcji enzymu monooksygenazy zawierającej flawinę 3 (FMO3), co prowadzi do nieprawidłowego metabolizmu trimetyloaminy (TMA).12 Chociaż stan ten jest stosunkowo rzadki, badania sugerują, że diagnoza może być często przeoczona przez lekarzy.3

Podejrzenie kliniczne

Diagnoza TMAU powinna być rozważana u pacjentów zgłaszających się z powodu uporczywego nieprzyjemnego zapachu ciała, szczególnie jeśli jest on opisywany jako „rybi”. W brytyjskim badaniu obejmującym 187 pacjentów zgłaszających się z powodu nieprzyjemnego zapachu ciała, u 17 opisano go jako rybi. Spośród tych 17 osób, u 11 zdiagnozowano trimetyloaminurię.4 Ważne jest, aby pamiętać, że samo podejrzenie oparte na zapachu nie jest wystarczające do postawienia diagnozy.5

Podczas badania klinicznego lekarz może (lub nie) wyczuć charakterystyczny zapach, co zależy od nasilenia objawów i momentu badania. W jednym z badań specjaliści chorób metabolicznych wykryli nieprzyjemny zapach ciała u dwojga dzieci, ale nie u 11 dorosłych pacjentów w momencie wizyty.6

Diagnostyka laboratoryjna

Podstawą diagnostyki TMAU jest analiza moczu z pomiarem stosunku trimetyloaminy (TMA) do N-tlenku trimetyloaminy (TMAO). W normalnych warunkach 80% TMA jest utleniana do TMAO i wydalana głównie z moczem. U osób z TMAU mniej niż 25% TMA ulega utlenieniu.78

Wyniki mogą być przedstawiane jako współczynnik utleniania według formuły:
TMAO/(TMAO+TMA) x 100%9

Interpretacja wyników
  • Współczynnik < 25% – typowy dla pacjentów z TMAU (homozygotyczne mutacje FMO3)10
  • Współczynnik 25-80% – może wskazywać na nosicielstwo (heterozygotyczne mutacje)11
  • Współczynnik > 80% (lub > 92% według niektórych źródeł) – osoby zdrowe12

1314

Metodyka badania

Istnieje kilka protokołów diagnostycznych stosowanych w celu wykrycia TMAU:

Test po obciążeniu substratem

Aby zmaksymalizować przepływ przez system utleniający i uwydatnić defekt metaboliczny, stosuje się następujące metody:

  • Test po posiłku rybnym – posiłek zawierający 300g ryb morskich, a następnie zbiórka moczu w czasie 2-12 godzin po posiłku lub alternatywnie, według protokołu z Nijmegen, zbiórka moczu przez 6-8 godzin po posiłku15
  • Test obciążenia choliną – pacjent wypija sok z dodaną choliną, a następnie zbiera mocz do analizy16
  • Test obciążenia trimetyloaminą – doustne podanie 600mg trimetyloaminy (u dorosłych)17

18

W przypadkach o łagodnym lub okresowym przebiegu zaleca się wykonanie testu po obciążeniu substratem, ponieważ przy normalnej diecie poziom TMA może być niedostatecznie podwyższony.19

Metody analityczne

Do pomiaru TMA i TMAO w moczu stosuje się różne metody analityczne:

  • Spektroskopia magnetycznego rezonansu jądrowego (1H NMR)
  • Chromatografia gazowa
  • Tandemowa spektrometria mas z jonizacją elektrosprejową
  • Spektrometria mas z jonizacją elektrosprejową i analizatorem czasu przelotu
  • Spektrometria mas z jonizacją laserową wspomaganą matrycą (MALDI-TOF)

20

Badania genetyczne

Badania genetyczne są dostępne i zalecane w przypadku pacjentów wydalających więcej niż 10% całkowitej TMA w postaci wolnej aminy.21 Trimetyloaminuria jest zwykle dziedziczona w sposób autosomalny recesywny, co oznacza, że obie kopie genu FMO3 w każdej komórce muszą posiadać mutacje.22

U pacjentów z ciężkimi i uporczywymi objawami oraz potwierdzonym nadmiernym wydalaniem TMA nawet przy niskim poziomie spożycia substratów, badania genetyczne mogą nie wnosić wiele do diagnozy.23 Jednak charakteryzacja mutacji genetycznej może być istotna w celach badawczych.24

Diagnostyka różnicowa

Przed postawieniem diagnozy TMAU należy wykluczyć inne, częstsze stany kliniczne, które mogą powodować nieprzyjemny zapach:

  • Zakażenia układu moczowego
  • Bakteryjna waginoza
  • Choroby dziąseł i przyzębia
  • Nadmierna potliwość (bromhidroza)
  • Zaawansowane choroby wątroby lub nerek
  • Kolonizacja dróg moczowych bakterią Aerococcus urinae (szczególnie u dzieci)

2526

Wyniki fałszywie dodatnie mogą wystąpić w powyższych stanach, gdzie podwyższony poziom TMA może być obecny w moczu bez podstawowego TMAU.27 Ponadto spożywanie niektórych warzyw z rodziny kapustowatych, szczególnie brukselki, może czasowo zmniejszyć aktywność FMO3 z powodu indoli zawartych w diecie – badania wykazały, że dieta zawierająca 300g brukselki dziennie przez 3 tygodnie tymczasowo zmniejszała zdolność FMO3 z ponad 90% do około 70%.28

Objawy przejściowe

Mayatepek i Kohlmuller (1998) opisali przypadki przejściowej trimetyloaminurii u dwojga dzieci, które wystąpiły bez niedoboru N-utleniania. Pokazuje to, że diagnoza zespołu zapachu rybnego powinna obejmować analizę wydalania z moczem nie tylko trimetyloaminy, ale także N-tlenku trimetyloaminy.29

Olfaktoryjny zespół odniesienia

Należy również rozważyć olfaktoryjny zespół odniesienia – stan, w którym występuje uporczywe fałszywe przekonanie i nadmierne zaabsorbowanie ideą wydzielania nieprawidłowego zapachu ciała, mimo braku obiektywnych dowodów.30

Znaczenie kliniczne wczesnej diagnozy

Choć manifestacje metaboliczne i kliniczne TMAU są zwykle uważane za łagodne, ponieważ nie wiążą się z dysfunkcją narządów, stan ten często pozostaje nierozpoznany przez lekarzy lub jest błędnie diagnozowany. Może to prowadzić do poważnych konsekwencji psychospołecznych, w tym wstydu, zakłopotania, niepowodzenia w utrzymywaniu relacji i izolacji społecznej.31 Dlatego też należy zachować niski próg podejrzenia TMAU u pacjentów z niewyjaśnionym nieprzyjemnym zapachem ciała, szczególnie jeśli jest on opisywany jako „rybi”.32

Potwierdzenie biochemiczne diagnozy TMAU można uzyskać tylko w przypadkach, gdy (i) zapach jest potwierdzony przez lekarza lub rodziców oraz (ii) nieprzyjemny zapach pojawia się w dzieciństwie.33

Centra diagnostyczne

Badania diagnostyczne w kierunku TMAU są wykonywane w specjalistycznych laboratoriach. Przykładowo, w USA wszystkie badania w kierunku TMAU są przeprowadzane bezpośrednio przez Laboratorium Genetyki Biochemicznej w Children’s Hospital Colorado w Aurora, CO.34

W przypadku podejrzenia TMAU pacjent powinien zostać skierowany do specjalisty z zakresu chorób metabolicznych, który może zlecić odpowiednie testy w celu potwierdzenia diagnozy.3536

Kolejne rozdziały

Zapraszamy do dalszego czytania naszego leksykonu.

Wybierz kolejny rozdział z menu poniżej, aby otworzyć nową podstronę kompedium wiedzy i uzyskać szczegółowe informację o leku, substancji lub chorobie.

  1. 10.04.2026
  2. www.leksykon.com.pl

Materiały źródłowe

  • #1 Trimethylaminuria – Wikipedia
    https://en.wikipedia.org/wiki/Trimethylaminuria
    Trimethylaminuria (TMAU), also known as fish odor syndrome or fish malodor syndrome, is a rare metabolic disorder that causes a defect in the normal production of an enzyme named flavin-containing monooxygenase 3 (FMO3). […] Measurement of urine for the ratio of trimethylamine to trimethylamine N-oxide is the standard screening test. A blood test is available to provide genetic analysis. The prominent enzyme responsible for TMA N-oxygenation is coded by the FMO3 gene. […] False positives can occur in the following conditions, where elevated TMA can be present in the urine without any underlying TMAU: urinary tract infection, bacterial vaginosis, cervical cancer, advanced liver or kidney disease. […] A similar foul-smelling odor of the urine has also been associated with colonization of the urinary tract with a bacterium called Aerococcus urinae, especially in children.
  • #2 Trimethylaminuria: MedlinePlus GeneticsLock
    https://medlineplus.gov/genetics/condition/trimethylaminuria/
    Trimethylaminuria is a disorder in which the body is unable to break down trimethylamine, a chemical compound that has a pungent odor. Trimethylamine has been described as smelling like rotten or decaying fish. As this compound builds up in the body, it causes affected people to give off a strong fishy odor in their sweat, urine, and breath. […] Trimethylaminuria is an uncommon genetic disorder; its incidence is unknown. […] Variants (also known as mutations) in the FMO3 gene cause trimethylaminuria. This gene provides instructions for making an enzyme that breaks down nitrogen-containing compounds from the diet, including trimethylamine. […] Most cases of trimethylaminuria appear to be inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have variants. […] Genetic Testing Registry: Trimethylaminuria. […] Clinical utility gene card for: trimethylaminuria.
  • #3 A Review of Trimethylaminuria: (Fish Odor Syndrome)
    https://pmc.ncbi.nlm.nih.gov/articles/PMC3848652/
    Trimethylaminuria, better known as fish odor syndrome, is a psychologically disabling condition in which a patient emits a foul odor, which resembles that of rotting fish. […] The condition is uncommon, but there has been recent research to suggest that the diagnosis may often be overlooked. […] While there is no cure, many simple treatment options exist that may drastically improve the quality of life of these patients. […] The diagnosis, which often eludes practitioners for years, is made on the basis of the clinical presentation and urinalysis. […] Urine can be analyzed for the concentration of both TMA and TMAO, and the results may be given as an oxidizing ratio based on the formula TMAO/(TMAO+TMA) x 100%. […] A ratio of less than 84 percent should be observed in an affected individual with two FMO3 inactivating mutations.
  • #4 Trimethylaminuria
    https://dermnetnz.org/topics/trimethylaminuria
    The diagnosis should be considered in patients presenting because of body odour, especially if described as fishy. In one study in the UK of 187 patients presenting due to body odour, 17 were described as fishy. Eleven of the 17 had trimethylaminura, but none of the others were affected with this condition. […] The diagnosis is confirmed on 24-hour urine collection while on a normal diet, and an 8-hour urine collection after either a marine fish meal (for children) or 600mg oral trimethylamine load (adults). Both trimethylamine and trimethylamine N-oxide should be measured. The trimethylamine challenge will detect both carriers and sufferers, as both will have a reduced conversion to trimethylamine N-oxide. Normal subjects will convert more than 80% of the trimethylamine to the N-oxide form, carriers convert less than 80% and sufferers less than 25% after the oral challenge. In menstruating females, the timing of the test is important as it may be a transient problem. […] The genetic mutation can be characterised, although this is generally for research purposes currently.
  • #5 Trimethylaminuria – Metabolic Support UKAccessibility ToolsIncrease TextDecrease TextGrayscaleHigh ContrastNegative ContrastLight BackgroundLinks UnderlineReadable FontReset
    https://metabolicsupportuk.org/condition/trimethylaminuria/
    How is it diagnosed? […] Diagnosis cannot be completed based on smell alone. A specialised urine test will be required to measure the amount of trimethylamine in your body. You may also be asked to take supplements and keep samples of your urine over a number of days in order to verify that Trimethylaminuria is the cause. […] Your medical team may also conduct genetic testing to confirm diagnosis of the disorder. […] Many other, more common, disorders and conditions also give off a strong odour, including urinary tract infections, bacterial vaginosis, gum disease, or body odour. Your medical team will have to rule out these possibilities first before diagnosing you with Trimethylaminuria.
  • #6 Diagnosis and phenotypic assessment of trimethylaminuria, and its treatment with riboflavin: 1H NMR spectroscopy and genetic testing | Orphanet Journal of Rare Diseases | Full Text
    https://ojrd.biomedcentral.com/articles/10.1186/s13023-019-1174-6
    The clinicians, who specialized in inherited metabolic diseases, detected an unpleasant body odor in the two children but not in the 11 adult patients at the time of the visit. […] The results obtained for each sample collected from the 2 children are presented in Table 4. For patient #12, all the ratios were out of the normal range, with the exception of TMAO/Cr, which suggests the persistence of residual oxidizing activity. […] The marked effect of vitamin B2 in both children was evidenced by the TMA/Cr ratio, which fell drastically within a few weeks. […] The biochemical validation of TMAU diagnosis can be made only for cases where (i) the odor is confirmed by the physician(s) or the parents, and (ii) the malodor begins during childhood.
  • #7 Diagnosis and phenotypic assessment of trimethylaminuria, and its treatment with riboflavin: 1H NMR spectroscopy and genetic testing | Orphanet Journal of Rare Diseases | Full Text
    https://ojrd.biomedcentral.com/articles/10.1186/s13023-019-1174-6
    Trimethylaminuria (TMAU) is a metabolic disorder characterized by the excessive excretion of the malodorous compound trimethylamine (TMA). The diagnosis of TMAU is challenging because this disorder is situated at the boundary between biochemistry and psychiatry. […] TMAU is diagnosed by measuring the TMAO:TMA ratio in the urine. In normal subjects, 80% of the TMA is oxidized and then excreted mainly in the urine; in individuals with TMAU, less than 25% of the TMA is oxidized. […] A variety of methods have been used to measure urine TMA and TMAO levels: proton nuclear magnetic resonance (1H NMR) spectroscopy, gas chromatography, electrospray ionization tandem mass spectrometry, direct infusion electrospray quadrupole time-of-flight mass spectrometry, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.
  • #8 A Review of Trimethylaminuria: (Fish Odor Syndrome)
    https://pmc.ncbi.nlm.nih.gov/articles/PMC3848652/
    Trimethylaminuria, better known as fish odor syndrome, is a psychologically disabling condition in which a patient emits a foul odor, which resembles that of rotting fish. […] The condition is uncommon, but there has been recent research to suggest that the diagnosis may often be overlooked. […] While there is no cure, many simple treatment options exist that may drastically improve the quality of life of these patients. […] The diagnosis, which often eludes practitioners for years, is made on the basis of the clinical presentation and urinalysis. […] Urine can be analyzed for the concentration of both TMA and TMAO, and the results may be given as an oxidizing ratio based on the formula TMAO/(TMAO+TMA) x 100%. […] A ratio of less than 84 percent should be observed in an affected individual with two FMO3 inactivating mutations.
  • #9 A Review of Trimethylaminuria: (Fish Odor Syndrome)
    https://pmc.ncbi.nlm.nih.gov/articles/PMC3848652/
    Trimethylaminuria, better known as fish odor syndrome, is a psychologically disabling condition in which a patient emits a foul odor, which resembles that of rotting fish. […] The condition is uncommon, but there has been recent research to suggest that the diagnosis may often be overlooked. […] While there is no cure, many simple treatment options exist that may drastically improve the quality of life of these patients. […] The diagnosis, which often eludes practitioners for years, is made on the basis of the clinical presentation and urinalysis. […] Urine can be analyzed for the concentration of both TMA and TMAO, and the results may be given as an oxidizing ratio based on the formula TMAO/(TMAO+TMA) x 100%. […] A ratio of less than 84 percent should be observed in an affected individual with two FMO3 inactivating mutations.
  • #10
    https://www.omim.org/entry/602079
    Ayesh et al. (1993) studied 187 subjects with suspected body malodor ascertained in response to a newspaper story concerning the fish-odor syndrome. Biochemical tests were performed in 156 of the patients and 5 families of 6 of the subjects with the fish-odor syndrome agreed to further tests. The fish-odor syndrome was diagnosed in 11 subjects; the percentage of total trimethylamine excreted in their urine samples that was oxidized to trimethylamine N-oxide was less than 55% under normal dietary conditions and less than 25% after oral challenge with trimethylamine. In normal subjects, more than 80% of trimethylamine was N-oxidized. All parents of 6 subjects with the syndrome who were tested showed impaired N-oxidation of excreted trimethylamine after oral challenge, indicating that they were heterozygous carriers of the allele for the syndrome. […] Mayatepek and Kohlmuller (1998) found that transient trimethylaminuria in 2 children occurred without N-oxidation deficiency. This demonstrated that a diagnosis of fish-odor syndrome should include the analysis of urinary excretion not only of trimethylamine but also of trimethylamine-N-oxide.
  • #11 Trimethylaminuria
    https://dermnetnz.org/topics/trimethylaminuria
    The diagnosis should be considered in patients presenting because of body odour, especially if described as fishy. In one study in the UK of 187 patients presenting due to body odour, 17 were described as fishy. Eleven of the 17 had trimethylaminura, but none of the others were affected with this condition. […] The diagnosis is confirmed on 24-hour urine collection while on a normal diet, and an 8-hour urine collection after either a marine fish meal (for children) or 600mg oral trimethylamine load (adults). Both trimethylamine and trimethylamine N-oxide should be measured. The trimethylamine challenge will detect both carriers and sufferers, as both will have a reduced conversion to trimethylamine N-oxide. Normal subjects will convert more than 80% of the trimethylamine to the N-oxide form, carriers convert less than 80% and sufferers less than 25% after the oral challenge. In menstruating females, the timing of the test is important as it may be a transient problem. […] The genetic mutation can be characterised, although this is generally for research purposes currently.
  • #12 A Review of Trimethylaminuria: (Fish Odor Syndrome)
    https://pmc.ncbi.nlm.nih.gov/articles/PMC3848652/
    Trimethylaminuria, better known as fish odor syndrome, is a psychologically disabling condition in which a patient emits a foul odor, which resembles that of rotting fish. […] The condition is uncommon, but there has been recent research to suggest that the diagnosis may often be overlooked. […] While there is no cure, many simple treatment options exist that may drastically improve the quality of life of these patients. […] The diagnosis, which often eludes practitioners for years, is made on the basis of the clinical presentation and urinalysis. […] Urine can be analyzed for the concentration of both TMA and TMAO, and the results may be given as an oxidizing ratio based on the formula TMAO/(TMAO+TMA) x 100%. […] A ratio of less than 84 percent should be observed in an affected individual with two FMO3 inactivating mutations.
  • #13 A Review of Trimethylaminuria: (Fish Odor Syndrome)
    https://pmc.ncbi.nlm.nih.gov/articles/PMC3848652/
    Trimethylaminuria, better known as fish odor syndrome, is a psychologically disabling condition in which a patient emits a foul odor, which resembles that of rotting fish. […] The condition is uncommon, but there has been recent research to suggest that the diagnosis may often be overlooked. […] While there is no cure, many simple treatment options exist that may drastically improve the quality of life of these patients. […] The diagnosis, which often eludes practitioners for years, is made on the basis of the clinical presentation and urinalysis. […] Urine can be analyzed for the concentration of both TMA and TMAO, and the results may be given as an oxidizing ratio based on the formula TMAO/(TMAO+TMA) x 100%. […] A ratio of less than 84 percent should be observed in an affected individual with two FMO3 inactivating mutations.
  • #14
    https://www.omim.org/entry/602079
    Ayesh et al. (1993) studied 187 subjects with suspected body malodor ascertained in response to a newspaper story concerning the fish-odor syndrome. Biochemical tests were performed in 156 of the patients and 5 families of 6 of the subjects with the fish-odor syndrome agreed to further tests. The fish-odor syndrome was diagnosed in 11 subjects; the percentage of total trimethylamine excreted in their urine samples that was oxidized to trimethylamine N-oxide was less than 55% under normal dietary conditions and less than 25% after oral challenge with trimethylamine. In normal subjects, more than 80% of trimethylamine was N-oxidized. All parents of 6 subjects with the syndrome who were tested showed impaired N-oxidation of excreted trimethylamine after oral challenge, indicating that they were heterozygous carriers of the allele for the syndrome. […] Mayatepek and Kohlmuller (1998) found that transient trimethylaminuria in 2 children occurred without N-oxidation deficiency. This demonstrated that a diagnosis of fish-odor syndrome should include the analysis of urinary excretion not only of trimethylamine but also of trimethylamine-N-oxide.
  • #15 Trimethylaminuria: Causes and Diagnosis of a Socially Distressing Condition
    https://pmc.ncbi.nlm.nih.gov/articles/PMC3052392/
    Trimethylaminuria is a disorder in which the volatile, fish-smelling compound, trimethylamine (TMA) accumulates and is excreted in the urine, but is also found in the sweat and breath of these patients. […] Diagnosis of trimethylaminuria requires the measurement of TMA and TMAO in urine, which should be collected after a high substrate meal in milder or intermittent cases, most simply, a marine-fish meal. […] In subjects with a history of malodour, urine can be readily analysed for TMA and TMAO. […] The most practical method of ensuring sufficient substrate is a 300 g marine fish meal followed by a random urine collection 212 hours after the meal or alternatively in the Nijmegen protocol, timed urine collection for 68 hours post meal. […] Because it is so important to ingest sufficient substrate to maximise flux through the oxidising system, several standardised methods of doing so have been used. […] In subjects with severe and persistent symptoms and confirmed excretion of excess TMA even at low levels of substrate intake, it is arguable whether mutation analysis adds a great deal to diagnosis.
  • #16 Monell’s TMAU Legacy – Monell Chemical Senses Center
    https://monell.org/tmau/
    Trimethylaminuria (TMAU), sometimes known as “Fish-Odor Syndrome,” is a genetically transmitted metabolic disorder. The main symptom of TMAU is a foul-smelling body odor. The odor can smell like fish in some patients and like garbage in others. […] TMAU is diagnosed using a biochemical laboratory test that measures the amount of trimethylamine in a patient’s urine after they drink juice containing added choline. […] All TMAU testing is handled directly through the Biochemical Genetics Laboratory at Children’s Hospital Colorado in Aurora, CO.
  • #17 Trimethylaminuria
    https://dermnetnz.org/topics/trimethylaminuria
    The diagnosis should be considered in patients presenting because of body odour, especially if described as fishy. In one study in the UK of 187 patients presenting due to body odour, 17 were described as fishy. Eleven of the 17 had trimethylaminura, but none of the others were affected with this condition. […] The diagnosis is confirmed on 24-hour urine collection while on a normal diet, and an 8-hour urine collection after either a marine fish meal (for children) or 600mg oral trimethylamine load (adults). Both trimethylamine and trimethylamine N-oxide should be measured. The trimethylamine challenge will detect both carriers and sufferers, as both will have a reduced conversion to trimethylamine N-oxide. Normal subjects will convert more than 80% of the trimethylamine to the N-oxide form, carriers convert less than 80% and sufferers less than 25% after the oral challenge. In menstruating females, the timing of the test is important as it may be a transient problem. […] The genetic mutation can be characterised, although this is generally for research purposes currently.
  • #18 Trimethylaminuria: Causes and Diagnosis of a Socially Distressing Condition
    https://pmc.ncbi.nlm.nih.gov/articles/PMC3052392/
    Trimethylaminuria is a disorder in which the volatile, fish-smelling compound, trimethylamine (TMA) accumulates and is excreted in the urine, but is also found in the sweat and breath of these patients. […] Diagnosis of trimethylaminuria requires the measurement of TMA and TMAO in urine, which should be collected after a high substrate meal in milder or intermittent cases, most simply, a marine-fish meal. […] In subjects with a history of malodour, urine can be readily analysed for TMA and TMAO. […] The most practical method of ensuring sufficient substrate is a 300 g marine fish meal followed by a random urine collection 212 hours after the meal or alternatively in the Nijmegen protocol, timed urine collection for 68 hours post meal. […] Because it is so important to ingest sufficient substrate to maximise flux through the oxidising system, several standardised methods of doing so have been used. […] In subjects with severe and persistent symptoms and confirmed excretion of excess TMA even at low levels of substrate intake, it is arguable whether mutation analysis adds a great deal to diagnosis.
  • #19 Trimethylaminuria: Causes and Diagnosis of a Socially Distressing Condition
    https://pmc.ncbi.nlm.nih.gov/articles/PMC3052392/
    Trimethylaminuria is a disorder in which the volatile, fish-smelling compound, trimethylamine (TMA) accumulates and is excreted in the urine, but is also found in the sweat and breath of these patients. […] Diagnosis of trimethylaminuria requires the measurement of TMA and TMAO in urine, which should be collected after a high substrate meal in milder or intermittent cases, most simply, a marine-fish meal. […] In subjects with a history of malodour, urine can be readily analysed for TMA and TMAO. […] The most practical method of ensuring sufficient substrate is a 300 g marine fish meal followed by a random urine collection 212 hours after the meal or alternatively in the Nijmegen protocol, timed urine collection for 68 hours post meal. […] Because it is so important to ingest sufficient substrate to maximise flux through the oxidising system, several standardised methods of doing so have been used. […] In subjects with severe and persistent symptoms and confirmed excretion of excess TMA even at low levels of substrate intake, it is arguable whether mutation analysis adds a great deal to diagnosis.
  • #20 Diagnosis and phenotypic assessment of trimethylaminuria, and its treatment with riboflavin: 1H NMR spectroscopy and genetic testing | Orphanet Journal of Rare Diseases | Full Text
    https://ojrd.biomedcentral.com/articles/10.1186/s13023-019-1174-6
    Trimethylaminuria (TMAU) is a metabolic disorder characterized by the excessive excretion of the malodorous compound trimethylamine (TMA). The diagnosis of TMAU is challenging because this disorder is situated at the boundary between biochemistry and psychiatry. […] TMAU is diagnosed by measuring the TMAO:TMA ratio in the urine. In normal subjects, 80% of the TMA is oxidized and then excreted mainly in the urine; in individuals with TMAU, less than 25% of the TMA is oxidized. […] A variety of methods have been used to measure urine TMA and TMAO levels: proton nuclear magnetic resonance (1H NMR) spectroscopy, gas chromatography, electrospray ionization tandem mass spectrometry, direct infusion electrospray quadrupole time-of-flight mass spectrometry, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.
  • #21 A Review of Trimethylaminuria: (Fish Odor Syndrome)
    https://pmc.ncbi.nlm.nih.gov/articles/PMC3848652/
    Trimethylaminuria, better known as fish odor syndrome, is a psychologically disabling condition in which a patient emits a foul odor, which resembles that of rotting fish. […] The condition is uncommon, but there has been recent research to suggest that the diagnosis may often be overlooked. […] While there is no cure, many simple treatment options exist that may drastically improve the quality of life of these patients. […] The diagnosis, which often eludes practitioners for years, is made on the basis of the clinical presentation and urinalysis. […] Urine can be analyzed for the concentration of both TMA and TMAO, and the results may be given as an oxidizing ratio based on the formula TMAO/(TMAO+TMA) x 100%. […] A ratio of less than 84 percent should be observed in an affected individual with two FMO3 inactivating mutations.
  • #22 Trimethylaminuria: MedlinePlus GeneticsLock
    https://medlineplus.gov/genetics/condition/trimethylaminuria/
    Trimethylaminuria is a disorder in which the body is unable to break down trimethylamine, a chemical compound that has a pungent odor. Trimethylamine has been described as smelling like rotten or decaying fish. As this compound builds up in the body, it causes affected people to give off a strong fishy odor in their sweat, urine, and breath. […] Trimethylaminuria is an uncommon genetic disorder; its incidence is unknown. […] Variants (also known as mutations) in the FMO3 gene cause trimethylaminuria. This gene provides instructions for making an enzyme that breaks down nitrogen-containing compounds from the diet, including trimethylamine. […] Most cases of trimethylaminuria appear to be inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have variants. […] Genetic Testing Registry: Trimethylaminuria. […] Clinical utility gene card for: trimethylaminuria.
  • #23 Trimethylaminuria: Causes and Diagnosis of a Socially Distressing Condition
    https://pmc.ncbi.nlm.nih.gov/articles/PMC3052392/
    Trimethylaminuria is a disorder in which the volatile, fish-smelling compound, trimethylamine (TMA) accumulates and is excreted in the urine, but is also found in the sweat and breath of these patients. […] Diagnosis of trimethylaminuria requires the measurement of TMA and TMAO in urine, which should be collected after a high substrate meal in milder or intermittent cases, most simply, a marine-fish meal. […] In subjects with a history of malodour, urine can be readily analysed for TMA and TMAO. […] The most practical method of ensuring sufficient substrate is a 300 g marine fish meal followed by a random urine collection 212 hours after the meal or alternatively in the Nijmegen protocol, timed urine collection for 68 hours post meal. […] Because it is so important to ingest sufficient substrate to maximise flux through the oxidising system, several standardised methods of doing so have been used. […] In subjects with severe and persistent symptoms and confirmed excretion of excess TMA even at low levels of substrate intake, it is arguable whether mutation analysis adds a great deal to diagnosis.
  • #24 Trimethylaminuria
    https://dermnetnz.org/topics/trimethylaminuria
    The diagnosis should be considered in patients presenting because of body odour, especially if described as fishy. In one study in the UK of 187 patients presenting due to body odour, 17 were described as fishy. Eleven of the 17 had trimethylaminura, but none of the others were affected with this condition. […] The diagnosis is confirmed on 24-hour urine collection while on a normal diet, and an 8-hour urine collection after either a marine fish meal (for children) or 600mg oral trimethylamine load (adults). Both trimethylamine and trimethylamine N-oxide should be measured. The trimethylamine challenge will detect both carriers and sufferers, as both will have a reduced conversion to trimethylamine N-oxide. Normal subjects will convert more than 80% of the trimethylamine to the N-oxide form, carriers convert less than 80% and sufferers less than 25% after the oral challenge. In menstruating females, the timing of the test is important as it may be a transient problem. […] The genetic mutation can be characterised, although this is generally for research purposes currently.
  • #25 Trimethylaminuria – Metabolic Support UKAccessibility ToolsIncrease TextDecrease TextGrayscaleHigh ContrastNegative ContrastLight BackgroundLinks UnderlineReadable FontReset
    https://metabolicsupportuk.org/condition/trimethylaminuria/
    How is it diagnosed? […] Diagnosis cannot be completed based on smell alone. A specialised urine test will be required to measure the amount of trimethylamine in your body. You may also be asked to take supplements and keep samples of your urine over a number of days in order to verify that Trimethylaminuria is the cause. […] Your medical team may also conduct genetic testing to confirm diagnosis of the disorder. […] Many other, more common, disorders and conditions also give off a strong odour, including urinary tract infections, bacterial vaginosis, gum disease, or body odour. Your medical team will have to rule out these possibilities first before diagnosing you with Trimethylaminuria.
  • #26 Trimethylaminuria – Wikipedia
    https://en.wikipedia.org/wiki/Trimethylaminuria
    Trimethylaminuria (TMAU), also known as fish odor syndrome or fish malodor syndrome, is a rare metabolic disorder that causes a defect in the normal production of an enzyme named flavin-containing monooxygenase 3 (FMO3). […] Measurement of urine for the ratio of trimethylamine to trimethylamine N-oxide is the standard screening test. A blood test is available to provide genetic analysis. The prominent enzyme responsible for TMA N-oxygenation is coded by the FMO3 gene. […] False positives can occur in the following conditions, where elevated TMA can be present in the urine without any underlying TMAU: urinary tract infection, bacterial vaginosis, cervical cancer, advanced liver or kidney disease. […] A similar foul-smelling odor of the urine has also been associated with colonization of the urinary tract with a bacterium called Aerococcus urinae, especially in children.
  • #27 Trimethylaminuria – Wikipedia
    https://en.wikipedia.org/wiki/Trimethylaminuria
    Trimethylaminuria (TMAU), also known as fish odor syndrome or fish malodor syndrome, is a rare metabolic disorder that causes a defect in the normal production of an enzyme named flavin-containing monooxygenase 3 (FMO3). […] Measurement of urine for the ratio of trimethylamine to trimethylamine N-oxide is the standard screening test. A blood test is available to provide genetic analysis. The prominent enzyme responsible for TMA N-oxygenation is coded by the FMO3 gene. […] False positives can occur in the following conditions, where elevated TMA can be present in the urine without any underlying TMAU: urinary tract infection, bacterial vaginosis, cervical cancer, advanced liver or kidney disease. […] A similar foul-smelling odor of the urine has also been associated with colonization of the urinary tract with a bacterium called Aerococcus urinae, especially in children.
  • #28 Trimethylaminuria – Wikipedia
    https://en.wikipedia.org/wiki/Trimethylaminuria
    Consumption of certain Brassica vegetables, in particular brussels sprouts, due to dietary indoles reducing FMO3 activity – research found that a diet including 300g of brussels sprouts per day for 3 weeks temporarily reduced FMO3 capability from 90%+ to ~70%. […] Olfactory reference syndrome is a condition where there is a persistent false belief and preoccupation with the idea of emitting an abnormal body odor. […] Affected individuals experience shame and embarrassment, fail to maintain relationships, avoid contact with people who comment on their condition, and are obsessive about masking the odour with hygiene products and even smoking. […] The metabolic and clinical manifestations of TMAU are generally regarded as benign, as there is no associated organ dysfunction. This designation, and the fact that the condition is often unrecognised by doctors, misdiagnosed and can have important ramifications including missed or delayed diagnosis.
  • #29
    https://www.omim.org/entry/602079
    Ayesh et al. (1993) studied 187 subjects with suspected body malodor ascertained in response to a newspaper story concerning the fish-odor syndrome. Biochemical tests were performed in 156 of the patients and 5 families of 6 of the subjects with the fish-odor syndrome agreed to further tests. The fish-odor syndrome was diagnosed in 11 subjects; the percentage of total trimethylamine excreted in their urine samples that was oxidized to trimethylamine N-oxide was less than 55% under normal dietary conditions and less than 25% after oral challenge with trimethylamine. In normal subjects, more than 80% of trimethylamine was N-oxidized. All parents of 6 subjects with the syndrome who were tested showed impaired N-oxidation of excreted trimethylamine after oral challenge, indicating that they were heterozygous carriers of the allele for the syndrome. […] Mayatepek and Kohlmuller (1998) found that transient trimethylaminuria in 2 children occurred without N-oxidation deficiency. This demonstrated that a diagnosis of fish-odor syndrome should include the analysis of urinary excretion not only of trimethylamine but also of trimethylamine-N-oxide.
  • #30 Trimethylaminuria – Wikipedia
    https://en.wikipedia.org/wiki/Trimethylaminuria
    Consumption of certain Brassica vegetables, in particular brussels sprouts, due to dietary indoles reducing FMO3 activity – research found that a diet including 300g of brussels sprouts per day for 3 weeks temporarily reduced FMO3 capability from 90%+ to ~70%. […] Olfactory reference syndrome is a condition where there is a persistent false belief and preoccupation with the idea of emitting an abnormal body odor. […] Affected individuals experience shame and embarrassment, fail to maintain relationships, avoid contact with people who comment on their condition, and are obsessive about masking the odour with hygiene products and even smoking. […] The metabolic and clinical manifestations of TMAU are generally regarded as benign, as there is no associated organ dysfunction. This designation, and the fact that the condition is often unrecognised by doctors, misdiagnosed and can have important ramifications including missed or delayed diagnosis.
  • #31 Trimethylaminuria – Wikipedia
    https://en.wikipedia.org/wiki/Trimethylaminuria
    Consumption of certain Brassica vegetables, in particular brussels sprouts, due to dietary indoles reducing FMO3 activity – research found that a diet including 300g of brussels sprouts per day for 3 weeks temporarily reduced FMO3 capability from 90%+ to ~70%. […] Olfactory reference syndrome is a condition where there is a persistent false belief and preoccupation with the idea of emitting an abnormal body odor. […] Affected individuals experience shame and embarrassment, fail to maintain relationships, avoid contact with people who comment on their condition, and are obsessive about masking the odour with hygiene products and even smoking. […] The metabolic and clinical manifestations of TMAU are generally regarded as benign, as there is no associated organ dysfunction. This designation, and the fact that the condition is often unrecognised by doctors, misdiagnosed and can have important ramifications including missed or delayed diagnosis.
  • #32 A Review of Trimethylaminuria: (Fish Odor Syndrome)
    https://pmc.ncbi.nlm.nih.gov/articles/PMC3848652/
    Conversely, individuals not afflicted with FOS should have a ratio of greater than 92 percent. […] Genetic testing is available and Shephard et al recommend molecular analysis for any patient excreting greater than 10 percent of total TMA as the free amine. […] The diagnosis can be established effectively by determining the oxidizing ratio of a urine specimen or by molecular means which are utilized in genetic testing. […] There are many options to reduce the severity of the condition, which range from simple lifestyle changes, such as washing with acidic soap and eating a choline-deficient diet to utilizing antibiotics and sequestering agents. […] A low threshold of suspicion for TMAU should be maintained by clinicians as this condition has a devastating effect on quality of life, reliable methods of diagnosis, and myriad treatment options.
  • #33 Diagnosis and phenotypic assessment of trimethylaminuria, and its treatment with riboflavin: 1H NMR spectroscopy and genetic testing | Orphanet Journal of Rare Diseases | Full Text
    https://ojrd.biomedcentral.com/articles/10.1186/s13023-019-1174-6
    The clinicians, who specialized in inherited metabolic diseases, detected an unpleasant body odor in the two children but not in the 11 adult patients at the time of the visit. […] The results obtained for each sample collected from the 2 children are presented in Table 4. For patient #12, all the ratios were out of the normal range, with the exception of TMAO/Cr, which suggests the persistence of residual oxidizing activity. […] The marked effect of vitamin B2 in both children was evidenced by the TMA/Cr ratio, which fell drastically within a few weeks. […] The biochemical validation of TMAU diagnosis can be made only for cases where (i) the odor is confirmed by the physician(s) or the parents, and (ii) the malodor begins during childhood.
  • #34 Monell’s TMAU Legacy – Monell Chemical Senses Center
    https://monell.org/tmau/
    Trimethylaminuria (TMAU), sometimes known as “Fish-Odor Syndrome,” is a genetically transmitted metabolic disorder. The main symptom of TMAU is a foul-smelling body odor. The odor can smell like fish in some patients and like garbage in others. […] TMAU is diagnosed using a biochemical laboratory test that measures the amount of trimethylamine in a patient’s urine after they drink juice containing added choline. […] All TMAU testing is handled directly through the Biochemical Genetics Laboratory at Children’s Hospital Colorado in Aurora, CO.
  • #35 Trimethylaminuria (’fish odour syndrome’) | Health Information from Mediclinic Pharmacy
    https://mediclinicpharmacy.com/nhs_conditions_trimethylaminuria
    Trimethylaminuria (TMAU) is an uncommon condition that causes an unpleasant, fishy smell. It’s also called „fish odour syndrome.” […] See a GP if you notice a strong, unpleasant smell that doesn’t go away. […] Tell your GP if you think it might be trimethylaminuria. It’s an uncommon condition and they may not have heard of it. […] They may refer you to a specialist for tests to check for the condition. […] In trimethylaminuria, the body is unable to turn a strong-smelling chemical called trimethylamine produced in the gut when bacteria break down certain foods into a different chemical that doesn’t smell. […] This means trimethylamine builds up in the body and gets into bodily fluids like sweat. […] Your doctor may recommend: short courses of antibiotics this can help reduce the amount of trimethylamine produced in your gut.
  • #36
    https://111.wales.nhs.uk/encyclopaedia/t/article/Trimethylaminuria(’fishodoursyndrome’)/
    Trimethylaminuria (TMAU) is an uncommon condition that causes an unpleasant, fishy smell. It’s also called „fish odour syndrome.” […] See a GP if you notice a strong, unpleasant smell that doesn’t go away. […] Tell your GP if you think it might be trimethylaminuria. It’s an uncommon condition and they may not have heard of it. […] They may refer you to a specialist for tests to check for the condition. […] Your doctor may recommend short courses of antibiotics this can help reduce the amount of trimethylamine produced in your gut.

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