Peripheral neuropathy of Machado-Joseph disease in Taiwan: a morphometric and genetic study

Machado-Joseph disease (MJD) is a dominantly inherited cerebellar ataxia associated with spasticity, ophthalmoplegia, dystonia and peripheral neuropathy. Presented here are 5 MJD cases. A morphometric analysis of the histopathology of their sural nerves was carried out to know the relationship between axon size and myelin thickness. MJD cases were identified by polymerase chain reaction. On the basis of the clinical symptoms, there was 1 type I, 2 type II and 2 type III patients. The sural nerves were biopsied for single-fiber, ultrastructural and morphometric analysis. Morphometric parameters such as fiber and axon sizes, myelin thickness and g ratio (axon diameter:fiber diameter) were estimated. The pathological features of the sural nerves in the 2 type III and 1 of the type II patients revealed a loss of myelinated and unmyelinated fibers, and the morphometry studies showed a decreased fiber density, the loss of large myelinated fibers, a smaller size of the axons with thinner myelin sheaths and an increased percentage of myelinated fibers with a g ratio (axon diameter:fiber diameter) above 0.7. However, only subtle pathological changes were noted in the type I patient and the remaining type II patient. Our findings suggested that there is a loss of large myelinated fibers and distal axonopathy with relative hypomyelination in the neuropathy of patients with MJD.