Association of rare variants in RNF213 with severe progression of intracranial artery stenosis in quasi–moyamoya disease

OBJECTIVE The genetic basis underlying the pathophysiology of quasi–moyamoya disease (qMMD) is unclear. Herein, the authors aimed to comprehensively analyze genetic variants in qMMD and investigate their association with clinical phenotypes, focusing on RNF213 and other moyamoya angiopathy (MMA)–related genes. METHODS The authors evaluated 14 consecutive cases of qMMD, whose underlying conditions included autoimmune disease, head irradiation, meningitis/pachymeningitis, and Turner syndrome, and 9 cases of hyperthyroidism-associated MMD (hMMD). The frequencies of RNF213 p.Arg4810Lys in qMMD and hMMD were each compared to those in healthy controls and in patients with MMD. Whole-exome sequencing was performed, and rare variants (RVs) or damaging variants were analyzed in RNF213 and 36 MMA-related genes. RESULTS The frequencies of p.Arg4810Lys were significantly higher in patients with qMMD (28.6%) and hMMD (33.3%) than in controls (1.1%; p < 0.001) and lower in the two former groups than in the MMD group (67.6%; p = 0.003 and 0.065, respectively). In qMMD, no significant clinical differences were observed based on the presence of p.Arg4810Lys. A novel RNF213 RV was identified in four cases with qMMD. These same cases also presented with significant worsening of intracranial main artery stenosis, which suggests a possible association between RNF213 RVs and the severe progression of qMMD. Among the 36 MMA-related genes, no variants correlated with specific phenotypes. CONCLUSIONS While the clinical implications of p.Arg4810Lys in cases with qMMD were not identified, the study findings suggest a potential association between RNF213 RVs and the significant progression of intracranial artery stenosis. Genetic analysis should not focus solely on p.Arg4810Lys but instead consider a comprehensive analysis of RNF213 for more accurate clinical prognostication of qMMD.