PLA2G6 and atypical Rett syndrome: Among SNV syndromes, Rett syndrome (4/62, 6.5%) was the most frequent, followed by autosomal dominant mental retardation type 35 (3/62, 4.8%), Okur-Chung neurodevelopment syndrome (OCNS) (3/62, 4.8%), Coffin-Lowry syndrome (2/62, 3.2%), Floating-Harbor syndrome (2/62, 3.2%), Sotos syndrome (2/62, 3.2%), Wiedemann-Steiner syndrome (2/62, 3.2%), X-linked mental retardation type 1 (2/62, 3.2%), neurodegeneration with brain iron accumulation type 2B (NBIA2B) (2/62, 3.2%), and SCN1A-related epileptic encephalopathy (2/62, 3.2%).