We find a novel deleterious WDR73 homozygous missense mutation in a consanguineous family. This is the first report on Chinese patients with WDR73 deficiency. We first suggest WDR73 to be a candidate gene of severe ID and cerebellar hypoplasia. The affected siblings in this report are the eldest living patients with WDR73 deficiency. This report is the first to suggest that microcephaly is a variable phenotype in WDR73-related disease.