Twenty out of those 42 patients were homozygous for the p.A307S mutation, 13 patients had mutations in EXOSC3, four patients harboured mutations in RARS2, one patient had SEPSECS mutations and one had mutations in AMPD2. We also identified hetero- or hemizygous CASK mutations in nine patients, indicating that this is a frequent cause of a condition similar to PCH. The gene discussed is CASK; the disease is pontocerebellar hypoplasia.