A spectrum of conditions caused by monoallelic pathogenic variants in ACTA2. Phenotypes can present in isolation or in combination and can include, but are not limited to: cardiovascular manifestations (heritable thoracic aortic aneurysm and dissection, coronary artery disease, patent ductus arteriosus, aortic pulmonary window, and/or early-onset atherosclerosis), smooth muscle cell dysfunction (hypoperistalsis, hydronephrosis and hydroureter, megacystis), ophthalmological manifestations (retinal vessel disease, congenital mydriasis and iris flocculi/hypoplasia), and a Moyamoya-like cerebrovascular disease. The disease is multisystemic smooth muscle dysfunction syndrome (Monarch Disease Ontology id MONDO_0013452). Also known as: ACTA2-related smooth muscle dysfunction syndrome.