Hypomyelinating leukoencephalopathy with paroxysmal tonic upgaze and absence of psychomotor development.

Hypomyelinating leukoencephalopathies are characterized by a substantial and permanent deficit in myelin deposition in the brain. Although our knowledge and understanding of the etiology of white matter diseases has progressively increased, many cases with this disorder remain undiagnosed, despite extensive evaluations. Recently, new disease entities have been defined by combining magnetic resonance imaging pattern recognition and clinical features. We describe a 1-year-old Ashkenazi Jewish girl with a hypomyelinating leukoencephalopathy, who presented in the neonatal period with episodes of sustained paroxysmal tonic upward gaze, roving eye movements, pendular nystagmus, and severe hypotonia, with the later appearance of pyramidal and extrapyramidal signs and no development. In addition, she has dysmorphic signs. This clinical picture is not consistent with any of the previously described hypomyelinating leukoencephalopathies and may represent a new entity.