Primary Autosomal Recessive Microcephaly (MCPH) is a rare neurodevelopmental disorder. Affected infants present with significantly small head circumferences and are mentally retarded. The prevalence ranges from 1 in 30,000 to 1 in 250,000 newborns worldwide of all forms of microcephaly that are present from birth. Ten subtypes of MCPH have been differentiated based on the 11 genes identified so far. MCPH may be caused by mutations in MCPH1, WDR62, CDK5RAP2, CEP152, ASPM, CENPJ, STIL, CEP63, CEP135, CASC5 or PHC1 genes. Diagnosis is based on clinical signs. Mutations in ASPM are the cause of microcephaly primary type 5 (MCPH5); also known as true microcephaly or microcephaly vera.

Mutation in the ASPM (Abnormal Spindle-Like, Microcephaly-Associated) gene is the main cause of primary autosomal recessive microcephaly (MCPH) disorder. More than 80 mutations have been identified in this gene, resulting in a short nonfunctional ASPM protein. Nonfunctional or partial protein produces few mature neurons, and the affected children born with a small brain.