Pontocerebellar hypoplasia type 1
(PCH1) is a genetic condition that affects the development of the brain. Individuals with this condition have an unusually small and underdeveloped cerebellum, which is the part of the brain that coordinates movement. A region of the brain called the pons also fails to develop properly. The pons, which is located at the base of the brain in an area called the brainstem, transmits signals from the cerebellum to the rest of the brain. Individuals with PCH1 also experience a degeneration of the anterior horn cells. Because of the anterior horn cell involvement, this condition bears a resemblance to infantile spinal muscular atrophy, with severe muscle weakness. Other signs and symptoms of PCH1 include very weak muscle tone (hypotonia), joint deformities called contractures, a small head size (microcephaly), and breathing problems that are present at birth. Mutations in the VRK1 gene have been identified in at least one family with PCH1. The condition is inherited in an autosomal recessive manner. Most children with PCH1 live only into infancy. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.