Megalencephaly-capillary malformation syndrome

Megalencephaly-capillary malformation (MCAP) syndrome, also known as macrocephaly-capillary malformation syndrome, is a rare and well described genetic disorder caused by somatic mutations in the PIK3CA gene on chromosome 3q26 and characterized by early brain overgrowth and body morphogenesis anomalies. 

Clinical presentation

MCAP syndrome is related to a unique variety of clinical findings1,2:

  • macrocephaly
  • cutaneous vascular malformations: usually involve body and face and,  less commonly, affect only midline face or body
  • distal limb anomalies: syndactyly, soft-tissue toe syndactyly, postaxial syndactyly, sandal-gap toes, brachydactyly, broad thumbs and toes, overlapping toes and hypoplastic toenails
  • somatic growth and asymmetry: birth weight, length 2 or more SD above the mean. 
    • associated with vascular anomalies
    • variable degrees of somatic asymmetry can be present, including hemihypertrophy and or leg length discrepancy
  • internal vascular abnormalities: a broad spectrum of internal vascular abnormalities are reported in the literature, involving abdominal, bronchial and heart vasculature
  • connective tissue dysplasia: skin hyperelasticity and joint hypermobility
  • dysmorphic craniofacial features:
    • dolichocephaly
    • frontal bossing
    • depressed nasal bridge
    • telecanthus or hypertelorism
  • development delay and intellectual disability

Radiographic features

CNS manifestations

Common findings include1,2:

Less common findings include:

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Article information

rID: 56415
Section: Syndromes
Synonyms or Alternate Spellings:
  • Macrocephaly-capillary malformation syndrome
  • Megalencephaly-capillary malformation (MCAP) syndrome
  • MCAP syndrome

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