The AB-variant of metachromatic leukodystrophy (postulated activator protein deficiency). Light and electron microscopic findings in a sural nerve biopsy.

THe histopathological findings in a sural nerve biopsy of a new distinct variant of metachromatic leukodystrophy (MLD) are compared to those of classical MLD. The clinical and histological features are typical of a sulfatide lipidosis, yet in vitro activities of arylsulfatases A and B and cerebroside sulfatase are normal. Intact skin fibroblasts, when cultured in a medium supplemented with labelled sulfatide, show impaired in vivo sulfatide hydrolysis. A deficiency of the requisite activator protein is postulated.