Prenatal Diagnosis of ACTG2 Visceral Myopathy Presented With Fetal Megacystis Identified in the Second Trimester

Variants of the ACTG2 gene cause autosomal dominant ACTG2 visceral myopathy, a disorder of smooth muscle dysfunction of the bladder and gastrointestinal system. Bladder involvement can behave as fetal megacystis (FM). We report four prenatal cases of ACTG2 visceral myopathy. All four cases presented with FM identified by ultrasound in the second trimester. All had invasive genetic investigations during pregnancy, and trio exome sequencing revealed likely pathogenic or pathogenic ACTG2 variants in the fetuses. Three of the four variants were de novo, and one was inherited form mother who had symptoms of smooth muscle dysfunction since childhood. ACTG2 visceral myopathy is the most concern in fetuses with isolated second-trimester megacystis. Genetic diagnosis of single gene disorders associated with FM is useful in parental counseling, pregnancy management and risk assessment of recurrence in future pregnancy.