Megacystis Associated With an Underlying ACTA2 Variant and Diagnosis of Multisystemic Smooth Muscle Dysfunction Syndrome: A Case Report.

Fetal megacystis, or an enlarged fetal bladder, is most often attributed to embryological defects, occurring early in gestation. Recent investigations have demonstrated that the underlying etiology of megacystis may be more myriad than originally thought. We present the third reported patient with megacystis due to an ACTA2 Arg179 substitution variant causing Multisystemic Smooth Muscle Dysfunction Syndrome. We also provide a description of pediatric evaluation and follow up. The growing number of cases in which this ACTA2 variant has been identified in fetal megacystis suggests that molecular sequencing is an appropriate consideration, particularly prenatally, when other features of Multisystemic Smooth Muscle Dysfunction Syndrome cannot be detected.