Isolated congenital microcephaly

Isolated congenital microcephaly, also known as primary microcephaly or microcephaly primary hereditary (MCPH), is a rare neurodevelopmental disorder characterized by a significantly reduced head circumference (at least 3 standard deviations below the mean for age and sex) that is present at birth. The condition results from impaired brain growth during fetal development, primarily affecting the cerebral cortex. Unlike syndromic forms of microcephaly, isolated congenital microcephaly occurs without other major malformations or progressive neurodegeneration. The central nervous system is the primary body system affected. The hallmark feature is a markedly small but normally proportioned brain. Individuals typically present with intellectual disability of variable severity, ranging from mild to severe. Speech and language delays are common. Some patients may experience seizures, although this is not universal. Motor development may also be delayed, though many individuals achieve independent ambulation. The facial appearance may include a sloping forehead and a proportionally small cranial vault relative to the face. Multiple genetic subtypes have been identified (MCPH1 through MCPH30 and beyond), with causative genes including ASPM, WDR62, CDK5RAP2, CASC5 (KNL1), CENPJ, STIL, CEP135, CEP152, and others. Most of these genes encode proteins involved in centrosome function, mitotic spindle formation, or DNA damage response — all critical for neuronal progenitor cell division during brain development. There is currently no cure or specific treatment for isolated congenital microcephaly. Management is supportive and multidisciplinary, including early intervention programs, speech therapy, physical therapy, occupational therapy, and seizure management when needed. Genetic counseling is recommended for affected families.

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