Pontocerebellar hypoplasia type 2: further clinical characterization and evidence of positive response of dyskinesia to levodopa.

Pontocerebellar hypoplasia type 2 (PCH2) is a very rare autosomal recessive disorder. We report two unrelated female patients born to consanguineous parents presenting with this condition. Patient 1 showed a classical clinical/neuroradiological phenotype of PCH2 with dyskinesia/dystonia. Patient 2 had a neonatal onset of PCH2 with polyhydramnios, apneic spells, myoclonus, and an akinetic/rigidity condition. Neuroradiologically, patient 2 showed extensive pancerebral degeneration. Based on these observations, and in accordance with the published cases, two groups of PCH2 patients may be defined: (a) patients with dyskinesia/dystonia, severe hypoplasia of the infratentorial structures and less severe involvement of the supratentorial brain; and (b) patients with polyhydramnios, neonatal onset with tremulousness (hyperekplexia), no spontaneous activity, absence of dyskinesia and pancerebral degeneration. Finally, we report a dramatic positive response of the patient with dyskinesia/dystonia to levodopa treatment, and discuss the associated physiopathological implications.