Megaloencephaly-Capillary Malformation (MCAP) Syndromeis one of the PIK3CA-related overgrowth syndromes (PROS).

Chromosome: 3q26.32

Gene: PIK3CA (phosphoinositide-3 kinase)

Genetic alteration: somatic mutation with postzygotic mosaic gain-of-function


Inheritance: not known to be inherited


Clinical features:

(1) megalencephaly or hemimegaloencephaly (HMEG)

(2) generalized overgrowth (macrosomia)

(3) cutaneous vascular malformations (of the face, cutis marmorata)

(4) cutaneous syndactyly, postaxial polydactyly or polysyndactyly

(5) subcutaneous lipomas

(6) hypoptonia

(7) seizures

(8) autistic and/or behavioral problems

(9) some level of intellectual disability

(10) feeding difficulties during infancy



(1) Wilm's tumor

(2) meningioma

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