MONDO_0016829 (familial visceral myopathy) is a rare hereditary myopathic degeneration of both gastrointestinal and urinary tracts that causes chronic intestinal pseudo-obstruction. It usually presents after the first decade of life with megaduodenum, megacystis and symptoms such as abdominal distension and/or pain, vomiting, constipation, diarrhea, dysphagia, and/or urinary tract infections.n. Also known as: familial hollow visceral myopathy, hereditary hollow visceral myopathy, megaduodenum and/or megacystis.