Pelizaeus-Merzbacher-like disease

Pelizaeus-Merzbacher-like disease (PMLD), also known as hypomyelinating leukodystrophy type 2 (HLD2), is a rare inherited disorder of the central nervous system that closely resembles Pelizaeus-Merzbacher disease (PMD) but is caused by different genetic mutations. While classic PMD is X-linked and caused by mutations in the PLP1 gene, PMLD is most commonly caused by autosomal recessive mutations in the GJC2 gene (formerly known as GJA12), which encodes the gap junction protein connexin 47. This protein plays a critical role in the formation and maintenance of myelin, the protective insulating sheath that surrounds nerve fibers in the brain and spinal cord. The disease belongs to the group of hypomyelinating leukodystrophies, characterized by a significant deficit in myelin formation. PMLD typically presents in infancy or early childhood with nystagmus (involuntary rhythmic eye movements), progressive spasticity, cerebellar ataxia (impaired coordination and balance), and significant motor developmental delay. Affected individuals often have hypotonia in early life that evolves into spasticity. Cognitive impairment of variable severity is common, and some patients may develop seizures. Brain MRI characteristically shows diffuse hypomyelination of the white matter, which is a hallmark finding shared with classic PMD. The disease affects both males and females equally, distinguishing it from X-linked PMD which predominantly affects males. There is currently no cure or disease-specific treatment for Pelizaeus-Merzbacher-like disease. Management is supportive and symptomatic, focusing on physical therapy to address motor impairments, occupational therapy, speech therapy, and medications to manage spasticity and seizures when present. Multidisciplinary care involving neurologists, rehabilitation specialists, and other healthcare providers is essential to optimize quality of life. Research into potential therapies, including approaches to promote myelination, is ongoing but remains in early stages.

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