Caprine β-mannosidosis, a fatal inherited deficiency of the lysosomal enzyme β-mannosidase, was diagnosed in neonatal female Nubian crossbred twin kids from a small herd near Guelph, Ontario. The kids had been tetraplegic since birth, with whole body tremors, abnormal nystagmus and an intention tremor of the head.
At necropsy, the histological lesions found consisted of widespread neuronal and visceral clear cytoplasmic vacuolation. Ultrastructurally, vacuoles were limited by a single membrane, and were empty or contained a small amount of amorphous dense material.
Biochemical assay of sera and tissues confirmed negligible levels of β-mannosidase activity, consistent with those of previously reported cases of caprine β-mannosidosis.
Vacuoles seen with light and electron microscopy are presumed to be lysosomes containing stored disaccharide and trisaccharide, the end products of incomplete catabolism of the oligosaccharide component of certain glycoproteins.