Background: Differences in the gastrointestinal manifestations have emerged between Swedish and Japanese familial amyloidotic polyneuropathy amyloidogenic transthyretin Valine30Methionine (FAP ATTR Val30Met) patients. To elucidate the cause of the differences, we investigated the associations between serotonin transporter gene-linked polymorphic region (5-HTTLPR) and/or catechol-O-methyl transferase (COMT) gene polymorphism and their gastrointestinal in these patients.
Methods: Twenty-six Swedish and 24 Japanese patients with gastrointestinal disturbances, in whom genetic material was available, were included in the study. The initial gastrointestinal manifestations of the disease were classified as constipation, constipation alternating with diarrhoea, continuous diarrhoea, and nausea/vomiting. 5-HTTLPR and COMT gene polymorphism were assessed by polymerase chain reaction and enzymatic digestion.
Results: A significantly higher LA allele frequency of 5-HTTLPR was noted in the Swedish population compared with that of the Japanese. Moreover, the LA allele frequency tended to be lower in the continuous diarrhoea group than in that of the remaining groups of both Swedish and Japanese patients. No association between COMT genotype and initial gastrointestinal symptoms was noted.
Conclusion: A high expression of serotonin transporter induced by LA allele of 5-HTTLPR may be one of the factors implicated with the inhibition of severe diarrhoea in early stages of Swedish FAP ATTR Val30Met patients.