In conclusion, we show that biallelic truncating and missense variants in PCDHGC4 cause a specific human phenotype characterized by neurodevelopmental delay, progressive microcephaly with mild to severe intellectual disability, global developmental delay, joint anomalies, and seizures, providing evidence that disease-causing variants in a single member of the clustered PCDH family are involved in the pathogenesis of a congenital disorder in humans. The gene discussed is PCDHGC4; the disease is Intellectual disability.