Patients present with short stature, generalized
hypotonia, and hyperreflexia. Mental retardation (of varying
severity), microcephaly, frontal bossing, hypertelorism, broad nasal root,
micrognathia or retrognathia, and failure to thrive appear to be common
findings. Magnetic resonance imaging of the brain reveals severe white matter
hypoplasia, extreme hypoplasia or even agenesis of the cerebellum and the
corpus callosum, and minor midline facial abnormalities.