Familial lysosomal storage disease with generalized vacuolization and sialic aciduria. Sporadic Salla disease

Two eight- and sixteen-year-old children with severe progressive neurologic disease revealed an ultrastructural finding of lysosomal vacuolization in mesenchymal or parenchymal cells of different organ biopsies (skin, muscle, nerve and liver), which may be very suggestive of mucolipidosis. However, in our patients biochemical tests available for these diseases yielded negative results, except for increased excretion of free sialic acid in urine and sialic acid storage in cultured fibroblasts. The clinical picture and the ultrastructural and biochemical findings were compatible with Salla disease, a rare lysosomal storage disease originally observed in Finland.