Pontocerebellar hypoplasia--how many types?

An original article describes a sibship with early fatal pontocerebellar hypoplasia of a yet unclassified type, with the accompanying features of polyhydramnios and neonatal myoclonus. Autopsy in one patient excluded spinal anterior horn involvement, which argues against pontocerebellar hypoplasia type I (PCH-1). The present PCH classification and literature are briefly reviewed. Four previous publications bear similarity to the present report. Definite classification as a genetically separate entity, however, remains elusive pending localization and identification of the gene(s) involved.