Posterior Column and Retinitis Pigmentosa

Posterior column ataxia with retinitis pigmentosa (PCARP) is an infantile-onset syndrome described in a single Spanish family that has clinical overlap with the other spinocerebellar ataxias. This disorder has onset between 2 and 14 years of age. Initial symptoms are progressive sensory ataxia and visual loss. Patients may have scoliosis, camptodactyly, achalasia and gastrointestinal dysmotility. On examination of vision in older children ring scotomata can be appreciated. There is retinitis pigmentosa, generalized arreflexia and loss of position sensation. Rhomberg sign is present. Pain and temperature sensation and hearing appear intact. Imaging studies do not show cerebellar atrophy, but spinal MRI sometimes reveals T2 signal hyperintensity in the dorsal columns. There is no cardiomyopathy, foot deformity, ophthalmoplegia, pyramidal signs or amyotrophy. Sural nerve biopsy shows loss of large myelinated fibers and preservation of unmyelinated axons. Linkage analysis has revealed that the locus for this disorder, called AXPC1, is on chromosome 1 at 1q31-32. Until the gene is identified the diagnosis can only be suspected by demonstration of genetic linkage of a kindred to the defined AXPC1 locus using polymorphic microsatellite markers for this region.