Angiokeratoma corporis diffusum with glycopeptiduria due to deficient lysosomal alpha-N-acetylgalactosaminidase activity. Clinical, morphologic, and biochemical studies.

BACKGROUND: Angiokeratoma corporis diffusum is a prominent cutaneous feature of certain lysosomal storage diseases. In this article, the clinical, morphologic, and biochemical features of a new, adult-onset lysosomal disease with angiokeratoma are described. OBSERVATIONS: A 46-year-old Japanese woman had diffuse angiokeratoma, mild intellectual impairment, and peripheral neuroaxonal degeneration. The angiokeratoma first appeared on her lower torso when she was 28 years old, and then it became diffusely distributed. Histopathologically, the telangiectasia had localized hyperkeratosis; ultrastructural examination revealed clear cytoplasmic vacuoles in all dermal cells, particularly in vascular and lymphatic endothelial cells and in eccrine sweat gland cells. The lysosomal pathologic features and increased urinary excretion of O-linked glycopeptides suggested the deficiency of a specific glycosidase. Enzyme analyses revealed less than 2% of normal alpha-N-acetylgalactosaminidase activity and the absence of immunodetectable enzyme protein. Her two unaffected children had half-normal alpha-N-acetylgalactosaminidase levels, consistent with the autosomal recessive inheritance of the enzymatic defect.
CONCLUSIONS: Since this enzyme deficiency was previously identified in patients with an infantile form of inherited neuroaxonal dystrophy, the occurrence of the enzymopathy in the 46-year-old proband described herein represents an adult-onset form of alpha-N-acetylgalactosaminidase deficiency. This newly recognized entity should be considered in the differential diagnosis of angiokeratoma corporis diffusum.