Polyneuropathy-hearing loss-ataxia-retinitis pigmentosa-cataract syndrome

Polyneuropathy-hearing loss-ataxia-retinitis pigmentosa-cataract syndrome (also known as pHARC syndrome) is an extremely rare autosomal recessive multisystem disorder characterized by the combination of peripheral polyneuropathy, sensorineural hearing loss, cerebellar ataxia, retinitis pigmentosa, and cataracts. This syndrome affects multiple body systems including the peripheral and central nervous systems, the auditory system, and the eyes. Patients typically develop progressive sensorimotor polyneuropathy leading to weakness and sensory deficits in the limbs, progressive hearing impairment, gait and coordination difficulties due to cerebellar dysfunction, progressive visual loss from retinitis pigmentosa (a degenerative condition of the retina), and lens opacities (cataracts) that further compromise vision. The syndrome has been linked to mutations in the ABHD12 gene, which encodes an enzyme involved in endocannabinoid and lysophosphatidylserine metabolism. Loss of function of this enzyme leads to the accumulation of specific lipid substrates that are thought to be neurotoxic, contributing to the progressive neurological and sensory deterioration observed in affected individuals. The onset of symptoms is typically in childhood or adolescence, with progressive worsening over time. There is currently no curative treatment for this condition. Management is supportive and multidisciplinary, involving neurologists, ophthalmologists, audiologists, and rehabilitation specialists. Interventions may include hearing aids or cochlear implants for hearing loss, cataract surgery for visual impairment, physical therapy and assistive devices for ataxia and polyneuropathy, and regular monitoring of disease progression. Genetic counseling is recommended for affected families.

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