Autopsy case of later-onset pontocerebellar hypoplasia type 1: pontine atrophy and pyramidal tract involvement.

The combination of pontocerebellar hypoplasia and anterior horn cell degeneration is classified as pontocerebellar hypoplasia type 1. Although most cases exhibit severe muscle weakness and hypotonia neonatally with short life spans, some cases exhibit a later onset with a longer life span and show cerebellar atrophy without pontine involvement. We present a child who exhibited neurological deterioration and progressive atrophy of the cerebellum and pons, with onset of symptoms at 20 months and death at 15 years of age. The pathological findings disclosed anterior horn cell degeneration and pyramidal tract involvement in addition to pontocerebellar atrophy, leading to the diagnosis of pontocerebellar hypoplasia type 1. The present case suggests that the degenerative pattern of later-onset pontocerebellar hypoplasia type 1 is similar to that of prenatal-onset cases. Further reports of later-onset cases with histopathological examination are required to elucidate the nosology and etiology of the disorder.