Pontocerebellar hypoplasia is a group of related brain development conditions that affect the pons and cerebellum, vital brain structures.
The pons helps transmit signals between the cerebellum and the rest of the brain, while the cerebellum coordinates movement. “Hypoplasia” means these regions don’t develop properly. This condition also stunts the growth of other brain parts, causing a small head (microcephaly) that becomes noticeable as the child grows slowly in infancy and early childhood. There are at least ten types of pontocerebellar hypoplasia, all showing impaired brain development, delayed development, movement issues, and intellectual disability. Brain problems are usually present at birth, and some can be detected before birth. Many affected children don’t live past infancy or childhood, though some reach adulthood. The major types are PCH1 and PCH2. PCH1 involves muscle movement problems due to nerve cell loss in the spinal cord, weak muscle tone, joint deformities, vision issues, and early breathing and feeding problems. PCH2 features a lack of voluntary motor skills, swallowing problems, no communication skills, and early jitteriness. Children also show abnormal movements, stiffness, impaired vision, and seizures.
This group of conditions is caused by pathogenic (disease-causing) variants in several genes and the test we offer covers VRK1 (type 1A), SEPSECS (type 2D), VPS53 (type 2E), and RARS2 (type 6). All exhibit autosomal recessive inheritance. This means that both parents must be carriers to have a 25% chance to have a child with the condition. The risk of being a carrier is based on a person’s ancestry or ethnic background. For example, individuals of Ashkenazi Jewish descent have a 1 in 308 chance to be a carrier for type 1A and individuals of Sephardic Jewish background have a 1 in 43 chance of being a carrier for type 2D.
Resources:
National Organization for Rare Disorders
Revised November 2023
