A Mild Variant of Pontocerebellar Hypoplasia Type 1 in a 12-Year-Old Indian Boy

Pontocerebellar hypoplasia is a heterogeneous group of disorders characterized by abnormally small cerebellum and brainstem. Pontocerebellar hypoplasia type 1 is associated with spinal anterior horn cell degeneration, microcephaly, congenital contractures, polyhydramnios, and respiratory insufficiency leading to death in infancy. Recently, however, the spectrum of this disease has been extended to include less severe variants, some of which are associated with minimal atrophy of the brainstem. In two reported cases of late-onset variant pontocerebellar hypoplasia, the siblings were alive at 9 years and 6 years, respectively, but were severely crippled and anarthric; they had features of anterior horn cell involvement and cerebellar atrophy but the brainstem was spared. The present case is that of a 12-year-old boy with early onset of anterior horn cell involvement and slowly progressive cerebellar ataxia who is still able to walk with support and speak in sentences. He was found to be devoid of the exon 7 and exon 8 deletion of the survival motor neuron gene seen in classical spinal muscular atrophy, and magnetic resonance imaging indicated marked atrophy of the cerebellar vermis and hemispheres, with minimal involvement of the brainstem. This form is apparently the mildest variant of pontocerebellar hypoplasia type 1 described to date.