Mechanisms of diarrhoea in myotonic dystrophy

Background Gastrointestinal (GI) symptoms are common in myotonic dystrophy (MD). Diarrhoea is one of the more disabling of these GI complaints. The mechanisms behind diarrhoea in MD have not previously been investigated systematically. Objective To elucidate the mechanisms behind diarrhoea in MD. Methods Twenty patients with MD and suffering from diarrhoea were investigated in order to detect malabsorption (blood tests and faecal fat excretion) and bile acid malabsorption {[ 75 Se]selenahomocholic acid-taurine (SeHCAT) retention) and to study intestinal morphology (duodenal and rectal biopsies). Results Two patients had deficiency of folic acid and four showed reduced levels of pancreatic isoamylase, but none of them had steatorrhoea. Two out of eight patients had abnormal bile acid breath tests with normal SeHCAT, indicating small bowel bacterial overgrowth and 12 displayed reduced SeHCAT retention. Duodenal biopsies were normal in eight patients and five out of nine rectal biopsies displayed slight inflammation. Conclusions A possible mechanism of diarrhoea in MD could be identified in most of the patients. Bile acid malabsorption seems to be a frequent cause and can be treated successfully.