Pontocerebellar hypoplasia type 5 (PCH5) is a very rare severe form of PCH (see this terme) with prenatal onset and characterized by fetal onset of clonus or seizures-like activity persisting in infancy and microencephaly leading to early postnatal death. There is significant overlap both in phenotype and in genotype between pontocerebellar hypoplasia types 4 and 5.
PCH5 is reported in 3 siblings to date.
PCH5, clinically resembling PCH4 (see this term), is characterized by fetal onset of clonus or seizure-like episodes, microcephaly, cerebellar hypoplasia persisting in infancy and microencephaly leading to early postnatal death.
PCH5 is caused by a compound heterozygosity for p.A307S plus splice site mutation in the gene. PCH5 transmission is autosomal recessive.
Clinically similar to PCH4, PCH5 is demonstrated on autopsy. MRI demonstrates inferior olivary dysplasia, and pontocerebellar hypoplasia with the vermis much more degenerated than cerebellar hemispheres. Pathological findings show and increased degeneration with Purkinje and granule cells in the vermis.
Antenatal diagnosis is possible by ultrasonic assessment of cerebellar width at 16-18 weeks gestation.
Last update: July 2013