The megalencephaly-polymicrogyria-polydactyly-hydrocephalus (MPPH) syndrome characterized by:
- Brain overgrowth or Megalencephaly (MEG) – often congenital
- Brain malformations – such as polymicrogyria
- Hydrocephalus – may require neurosurgical intervention
- Extra digits (either fingers or toes)
Mutations are most often de novo (i.e. not inherited)