Rett-like features and cortical visual impairment in a Japanese patient with HECW2 mutation.

Numerous genetic syndromes that include intellectual disability (ID) have been reported. Recently, HECW2 mutations were detected in patients with ID and growth development disorders. Four de novo missense mutations have been reported. Here, we report a Japanese girl with Rett-like symptoms of severe ID, hypotonia, refractory epilepsy, and stereotypical hand movement (hand tapping, flapping, and wringing) after the age of 1 year. Characteristically, she had cortical visual impairment. She had difficulty swallowing since the age of 4 years, and diminished activity was noticeable since the age of 12 years, suggesting neurodevelopmental regression. She has no acquired microcephaly, and brain magnetic resonance imaging showed non-specific mild cerebral and cerebellar atrophy without progression over time. Genetic analyses of MECP2, CDKL5, and FOXG1 were negative. Whole-exome sequencing analysis revealed a known de novo mutation (c.3988C > T) in HECW2. The characteristics of her clinical symptoms are severe cortical visual impairment and Rett-like phenotype such as involuntary movements and regression. This is the first report that patients with HECW2 mutation could show Rett-like feature.