NEUROAXONAL DYSTROPHY IN A GROUP OF RELATED CATS

A syndrome resembling previously described feline hereditary neuroaxon al dystrophy (FHND) was diagnosed in a litter of cats. The disorder wa s characterized by a sudden onset of hind limb ataxia that slowly prog ressed to hind limb paresis and paralysis. The cats were between 6 and 9 months old when clinical signs were first noted. Histologically, th ere was marked ballooning of axonal processes, with spheroid formation and vacuolation in specific regions of the brain and spinal cord. Som e dystrophic axons contained a central periodic acid-Schiff (PAS)-posi tive core. Neuronal loss and gliosis were seen in certain brain stem n uclei, spinal cord nuclei, and the cerebellum. Ultrastructurally, ther e was hypomyelination and dysmyelination of affected axons. The PAS-po sitive core in dystrophic axons corresponded ultrastructurally with ac cumulations of electrondense, flocculent, amorphous material. In addit ion, these axons contained membrane-bound osmiophilic bodies and large nonmembrane-bound vacuoles. The syndrome in this report differs from the previously described FHND in that no inner ear involvement was see n and onset of clinical signs occurred at a later age. In addition, al though some of the affected cats did have diluted coat colors, abnorma l coat color was not always associated with clinical disease. This dis ease is similar to juvenile neuroaxonal dystrophy in children and to n euroaxonal dystrophies described in horses, dogs, cattle, and sheep.