A de novo TUBB4A mutation in a patient with hypomyelination mimicking Pelizaeus-Merzbacher disease

Abstract

Objective: Hypomyelinating leukoencephalopathy is a heterogeneous disorder caused by mutations in several-different genes. Clinical entity of hypomyelination with atrophy of the basal ganglia and cerebellum (H-ABC) is one of them.

Method: A male patient showed pendular nystagmus, infantile hypotonia, an abnormal pattern of brain auditory evoked potential, and hypomyelination on brain magnetic resonance imaging, which suggested Pelizaeus-Merzbacher disease (PMD) as the candidate diagnosis; however, no abnormality was found in the proteolipid protein 1 gene (PLP1) that is responsible for PMD. Whole exome sequencing was performed to identify pathogenic mutations in this patient.

Results: A de novo mutation was identified in the tubulin 4a gene (TUBB4A), which has been recently reported to be associated with H-ABC. Although the patient did not show any neurological features suggesting H-ABC, such as extrapyramidal or cerebellar signs, radiological findings demonstrated the finding of cerebellar atrophy at the age of 36months.

Conclusion: This study suggested us the difficulty of clinical diagnosis for H-ABC early in the life of the patient, which makes predication of prognosis and genetic counseling difficult.

Keywords: Genetic counseling; Hypomyelinating leukoencephalopathy; Hypomyelination with atrophy of the basal ganglia and cerebellum (H-ABC); Pelizaeus–Merzbacher disease (PMD); TUBB4A.