Multisystemic smooth muscle dysfunction syndrome

Multisystemic smooth muscle dysfunction syndrome (MSMDS) is a genetic disorder caused by R179 missense mutations in the ACTA2 gene. Initially described as a case report in 1999, it was characterized in 2010 as a syndrome of congenital mydriasis, patent ductus arteriosus, and aneurysmal arterial disease—in particular aortic and thoracic aneurysms. The disorder has variable penetrance, ranging from severely symptomatic and fatal in early neonatal period to a more benign and manageable course with surgical intervention.