Child Neurology: Hypotonia and Delayed Teeth Eruption in a 2-Year-Old Girl.

POLR3-related disorders are rare hypomyelinating leukodystrophies associated with hypodontia. We present a female patient, who was referred to pediatric neurology at 2 years of age for tremor, low tone, and motor delays. In addition, she was noted to have a delay in her teeth eruption and myopia. Neurologic examination was significant for ataxic features and global developmental delay. Laboratory workup was unrevealing. MRI was significant for hypomyelination. Genetic testing confirmed a pathogenic variant of POLR3-related leukodystrophies should be considered in patients who present with hypotonia, ataxia, and hypodontia. There are many different subtypes of POLR-related leukodystrophies each with distinguishing phenotypic and radiographic features. Although MRI can be helpful in initial evaluation, genetic testing is needed for confirmatory diagnosis and to guide prognosis.