Human β‐mannosidase deficiency associated with peripheral neuropathy

Human beta-mannosidosis is an inherited lysosomal storage disorder described in only seven families. We present a further case in a black African 14-year-old boy with severely deficient beta-mannosidase activity, bilateral thenar and hypothenar amyotrophy, electrophysiologically demonstrable demyelinating peripheral neuropathy, and cytoplasmic vacuolation of skin fibroblasts and lymphoid cells. The clinical and biochemical features of our patient are compared to those of previously reported patients.