Biochemical comparison of the dysmorphic type with the normosomatic type of sialidosis

Two types of juvenile sialidosis, the dysmorphic type and the normosomatic type, were studied biochemically to establish the differences between these two types. Accumulation of sialic acid-containing substance in the urine and fibroblasts was more marked in the dysmorphic type than in the normosomatic type. The dysmorphic type showed complete sialidase (neuraminidase, N-acetylneuraminic acid hydrolase, EC 3.2.1.18) deficiency in fibroblasts with various substrates, while the normosomatic type showed partial sialidase deficiency. Although the normosomatic type may be an incomplete form of the dysmorphic type from the standpoint of sialidase deficiency, the dysmorphic type also has a beta-galactosidase deficiency. Further studies are necessary to elucidate whether or not the normosomatic type is an incomplete form of the dysmorphic type.