ACTA1 and multisystemic smooth muscle dysfunction syndrome: Subsequently, Milewicz et al. and others described a highly penetrant phenotype of a Multisystemic Smooth Muscle Dysfunction Syndrome (MSMDS, OMIM#613834) associated, specifically, with the Arg179 substitutions in α-SMA; characterised by congenital mydriasis, retinal artery tortuosity, livedo reticularis, ascending TAAD, coronary artery disease, PDA, APW, cerebral arteriopathy resembling but distinct from the classic moyamoya disease (MMD), periventricular white matter lesions, hypotonic bladder, malrotation and hypoperistalsis of the intestinal tract, and pulmonary hypertension [12–14].