Megalencephaly-capillary malformation-polymicrogyria syndrome

PIK3CA-associated segmental overgrowth includes disorders of brain (e.g., MCAP [megalencephaly-capillary malformation] syndrome, hemimegalencephaly); and segmental body overgrowth (e.g., CLOVES [congenital lipomatous asymmetric overgrowth of the trunk, lymphatic, capillary, venous, and combined-type vascular malformations, epidermal nevi, skeletal and spinal anomalies] syndrome, fibroadipose hyperplasia [FH]). Heterozygous (usually somatic mosaic) pathogenic variants of PIK3CA are causative. MCAP syndrome is characterized by the major findings of (1) megalencephaly (MEG) or hemimegalencephaly (HMEG) associated with neurologic findings of hypotonia, seizures, and mild to severe intellectual disability; and (2) cutaneous capillary malformations with focal or generalized somatic overgrowth. Additional findings can include digital anomalies (syndactyly, polydactyly), cortical malformations – most distinctively polymicrogyria (PMG); and variable connective tissue dysplasia. CLOVES (or CLOVE) syndrome and fibroadipose hyperplasia (FH) may be associated with (1) MEG or HMEG; and (2) patchy segmental overgrowth associated with skeletal anomalies, lipomatosis, vascular malformations, and epidermal nevi.

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