Infantile neuroaxonal dystrophy and Giant Axonal Neuropathy - overlap diseases of neuronal cytoskeletal elements in childhood?

Giant axonal neuropathy (GAN) and infantile neuroaxonal dystrophy (INAD) ar e two progressive neurodegenerative disorders of childhood that have consid erable clinical as well as histological overlap but are believed to be ultr astructurally distinct. The clinicopathological and ultrastructural feature s of three cases of INAD, two of whom are siblings and one case of GAN are described. The sm al nerve: biopsies in all four cases were essentially sim ilar on light microscopy revealing giant axons. On electron microscopy, the findings in the case of GAN were typical with dense accumulation of neurof ilaments within the giant axons. In the three cases of INAD, too, in additi on to accumulation of mitochondria and organelles with vesiculotubular prof iles, a similar increase in neurofilaments was evident. We, therefore, beli eve that these two disorders may represent a spectrum in evolution of inter mediate filament pathology with various organelles participating in the tem poral evolution of the disease process.