RET promoter variations in familial African degenerative leiomyopathy (ADL): first report of a possible genetic-environmental interaction.

African degenerative leiomyopathy (ADL, DL, Bantu pseudo-Hirschsprung's disease) is a distinctive visceral myopathy, of unknown etiology, occurring in Africa. It has a classical clinical and histologic picture in young indigenous African children. It presents as intestinal pseudo-obstruction with a massive megacolon due to degeneration of smooth muscle without aganglionosis. Because of its late presentation and geographical and ethnic distribution, it is thought to be an acquired degenerative hollow visceral myopathy. Only one previous report of familial recurrence exists. The main Hirschsprung susceptibility gene RET is a potential candidate gene in this condition, because of its role in the development of the intrinsic innervation and ganglia of the smooth muscle layers of the gastro-intestinal tract. We report a second case of familial ADL recurrence and explore possible etiologic causes including variations of the RET gene. Multiple variations in the RET promoter were identified in this case which leads to the possibility of a genetic-environmental predisposition for this condition. We therefore hypothesize that RET may play a modulating role in ADL susceptibility (and possibly other visceral myopathies). It is possible that subtle malformations in the ENS may result from RET dysfunction which then predisposes the individual to environmental influences which initiate the later onset of muscle degeneration.