megacystis-microcolon-intestinal hypoperistalsis syndrome familial visceral myopathy 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. GARD:0003443 ICD10:K56.0 ICD9:359.89 MONDO:0016829 Megaduodenum and/or megacystis Orphanet:2604 SCTID:63684002 UMLS:C0266833 UMLS:C1835084 UMLS:CN202146 familial hollow visceral myopathy hereditary hollow visceral myopathy pseudoobstruction idiopathic intestinal visceral myopathy familial