An Overview of Genetics of Moyamoya: Beyond RNF213 Gene.

Moyamoya angiopathy (MMA) is a rare, chronic progressive cerebrovascular condition characterized by bilateral stenosis or occlusion of the terminal internal carotid arteries and their major branches. This progressive occlusion triggers the development of telangiectatic and fragile vessels at the base of the brain, creating the characteristic angiographic appearance of a "puff of smoke." Depending on the etiology, MMA is classified as Moyamoya Disease (MMD) when idiopathic and primary or Moyamoya Syndrome (MMS) when associated with underlying systemic conditions. While the RNF213 gene, particularly the p.R4810K variant, is recognized as the major susceptibility locus for MMD in East Asian populations, it does not fully account for the global genetic landscape or the phenotypic diversity of the disease. This review provides a comprehensive overview of the genetic architecture of the entire MMA spectrum, exploring loci beyond RNF213. We analyze the role of genes involved in vascular smooth muscle cell contractility (ACTA2, MYH11), TGF-β signaling, and DNA repair mechanisms that drive MMS, alongside the genetic basis of syndromic forms associated with neurofibromatosis type 1, trisomy 21, and RASopathies. Understanding these diverse genetic drivers is crucial for early diagnosis, risk stratification, and the development of targeted molecular therapies.