Newly described recessive MYH11 disorder with clinical overlap of Multisystemic smooth muscle dysfunction and Megacystis microcolon hypoperistalsis syndromes.

We describe a neonatal patient with fixed dilated pupils and pulmonary, bladder, and bowel dysfunction suspicious for the presence of ACTA2 R179 mediated multisystemic smooth muscle dysfunction syndrome. Whole exome sequencing revealed compound heterozygous mutations in MYH11 after ACTA2 specific testing revealed no abnormalities. The child lived until 18 months of age and represents the only reported case of an MYH11 compound heterozygote with widespread smooth muscle dysfunction.