Type of disease: Rare conditions

Hemimegalencephaly is a rare malformation involving one side of the brain. It may occur alone or in association with epidermal nevus syndrome, Proteus syndrome, or Klippel-Trenaunay syndrome. It usually causes partial epilepsy, which may be treated with hemispherectomy. Hemimegalencephaly can also cause intellectual disability and impair normal movement on the side of the body opposite of the malformation. Symptoms range from mild to severe. The cause of this condition is not fully understood, but involves a disturbance of cells early in development and likely involves genes involved in patterning and symmetry.

Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.

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