Expanding the Spectrum of KDM5C Neurodevelopmental Disorder: A Novel De Novo Stop Variant in a Young Woman and Emerging Genotype–Phenotype Correlations

Abstract

As a consequence of the implementation of NGS technologies, the diagnostic yield of neurodevelopmental disorders has dramatically increased during the past two decades. Among neurodevelopmental genes, transcription-related genes and chromatin remodeling genes are the most represented category of disease-causing genes. Indeed, the term “chromatinopathies” is now widely used to describe epigenetic disorders caused by mutations in these genes. We hereby describe a twenty-seven-year-old female patient diagnosed with moderate intellectual disability comorbid with other neuropsychiatric and behavioral issues carrying a de novo heterozygous stop variant in the KDM5C gene (NM_004187.5: c. 3847G>T, p.Glu1283*), encoding a histone demethylase that specifically acts on the H3K4 lysines. The gene is located on the X chromosome and has been associated with Claes–Jensen-type intellectual disability, an X-linked syndromic disorder. We discuss our case in relation to previously reported affected females harboring pathogenic mutations in the KDM5C gene with the objective of delineating genotype–phenotype correlations and further defining a common recognizable phenotype. We also highlight the importance of reverse phenotyping in relation to whole-exome sequencing results.