A de novo GFAP variant, p.R376W, was identified in a child presenting with hypotonia, developmental delay, and abnormal brain MRI. Following the 2015 ACMG variant classification guidelines and the functional studies showing protein aggregate formation in vitro, p.R376W should be classified as a pathogenic variant, causative for Alexander disease.
Keywords: Alexander disease; developmental delay disorders; glial fibrillary acid protein; leukoencephalopathies; muscle hypotonia; paralog analysis.