Sialidosis (mucolipidosis I).

The term "sialidosis" is suggested for the deficiency of alpha-neuraminidase activity in peripheral leukocytes and cultured fibroblasts which results in a considerable urinary excretion of sialyl-oligosaccharides. This defect was found in two siblings with a mild form of mucolipidosis I. 12 sialyl-acid rich oligosacharides have been isolated from the urine of the patients. The structure of ten of them has been determined. The studies of the patients show a remarkable variability of the clinical expression of this disease. The two siblings exhibited a progressive reduction of visual acuity, red-green blindness, a bilateral cherry red macular spot, punctate opacities of the lens, and minimal neurological symptoms. Morphologically, vacuolized lymphocytes, refringent inclusions in cultured fibroblasts, numerous cytoplasmatic inclusions containing a fine protein-like reticulum and some osmiophilic granules mainly in Kupffer's cells were found.