Differing phenotypes of Moyamoya disease in a familial case involving heterozygous c.14429G > A variant in RNF213

Moyamoya disease (MMD) is a chronic steno-occlusive arteriopathy involving the development of abnormal collateral vessels. Ring finger protein (RNF213) on the 17q25.3 locus was identified as an MMD-susceptibility gene in East Asian populations. We report a 5-year-old Japanese boy diagnosed with cerebral infarction and unilateral MMD. Magnetic resonance angiography (MRA) showed severe stenosis of the left internal carotid artery (ICA), terminal portion of the left ICA, and left origin of the posterior cerebral artery. Genetic testing indicated a heterozygous c.14429G>A (formerly described as c.14576G>A) variant in RNF213. The boy's mother had no neurological symptoms, but sequencing of RNF213 showed the same variant, and MRA indicated stenosis of the terminal bilateral ICA. This is the first report, to our knowledge, of different MMD phenotypes in a familial case involving the same heterozygous c.14429G>A variant in RNF213. Genetic testing for RNF213 is suggested for family member screening.