Trimethylaminuria and Vascular Complications

Background: Trimethylaminuria (Fish-Odour Syndrome) is a rare metabolic disorder characterized by an unpleasant odour in body secretions similar to rotting fish. The disorder is most commonly caused from mutations affecting the Flavin containing monooxygenase 3 (FMO3) gene, the vital enzyme for the metabolism of trimethylamine. Although uncommon, it is important to be conscious of this condition, which can be devastating psychosocially even with reliable diagnostic tests. We present here an individual with this syndrome who, in addition to the psychosocial difficulties, presented physical complications that we relate to the disease’s physiopathology. Case: R.M.F., 56 years old, lawyer, self-diagnosed at 25 after identifying himself with a disease description in a local newspaper. He describes fish odour symptoms from infancy and his mother used to demand excessive hygiene habits. He has always suffered from social disturbances. At 44, a physician’s investigation detected FMO3 mutation. The patient is not obese, has never smoked and denies any comorbidity, except erectile dysfunction for 10 years. He presented 4 years ago extensive acute venous thrombosis in the right lower limb femoral veins, lateral and medial gastrocnemius, solar and fibular popliteal veins. Laboratory investigation excluded other causes and negative antibodies. Besides, ENMG confirmed last year peripheral motor sensitive polyneuropathy, axonal pattern, distal both lower extremities. The patient failed treatment with modifications in diet and hygiene, but achieved symptomatic improvement after metronidazole. Genetic analysis showed a new homozygotic variant in the FMO3 gene, with substitution of adenine for cytosine and exchange of Threonine for proline at position 307 of the FMO3 protein with protein dysfunction computably predicted. Comments: Considering the deep venous thrombosis and symmetrical peripheral neuropathy developed by the patient, we searched for a possible association with TMAU but we did not find previous reports. However, Weifei Zhu et al. (Circulation, 135(17), 1671–73,2017) have shown TMAO generated by gut microbes contributing to platelet hyper reactivity and causing a prothrombotic phenotype in vivo. Plasma TMAO levels could predict incident thrombosis risk. Also, direct TMAO exposure enhanced platelet activation from multiple agonists stimulus. Although the “chemical sensor” for TMAO within platelets remains unknown, these findings could increase our understanding of the relationship between TMAO and CVD risk. Although the disorder might not appear to be a significant health problem, its social and psychological burden can be devastating, since the few treatments available provide modest benefits. In addition, it may be associated with other complications, including CVD, to which we would like to draw attention with this report