Reasons for transient TMAU episodes

Dr Dolphin was part of the team who first demonstrated that mutations in the FMO3 gene are the cause of the inherited (primary form) of TMAU.

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Reasons for transient TMAU episodes

Postby admin » Thu Jul 07, 2011 9:17 am

This is my question::
"Although I have a defective FMO3 Gene I was completely asymptomatic throughout my entire life until a few years before being eventually diagnosed.

I have had people say to me that I probably always had the symptoms but no one had ever said anything - I know that's not the case as we all know school children home in on others weaknesses, plus I was a policeman for a good few years before anyone started noticing and they are merciless when it comes to mickey taking.

I have never had any major desease that I know of though the police was a highly stressful job.

Was the defect always (ie a static non changing defect) there in the gene or can it change throughout life?

If it does change do we know what my cause this (liver desease etc)?

Dr Dolphins Reply


To answer your question below. You inherited a faulty copy of the gene from either your Mum or Dad and a normal copy from your other parent - so you're a so-called heterozygote.

This 'genotype' doesn't change as you age so you'll always be a heterozygote. However, as you only have one 'normal' FMO3 gene copy the actual amount of FMO3 enzyme in the liver will always be somewhat less than in an individual with two 'normal' copies. As such whenever the FMO3 capacity became/becomes overloaded you might experince a TMAU episode.

There could be many reasons why these episodes have only been evident in later life - difficult to say what it/they might be - but they're almost certainly not genetic in the sense that the sequence of your two FMO3 gene copies could change. Its possible that as you got older the FMO3 content in the liver dropped slightly for no particular reason - liver enzyme levels do fluctuate with age - and so just dipped below that point where, on occasion, it could handle all the TMA that was entering the liver. Other factors, such as liver disease, would also cause the FMO3 to drop. Also, its pretty well documented that common viral infections such as flu will cause these enzymes, including FMO3, to drop for the period of the illness and again this might result in a brief TMAU episode.
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