[Mucolipidosis II (I cell disease): a sialidosis?].

I cell disease is characterised by loss of lysosomal enzymes from fibroblasts with accumulation of the same enzymes in the surrounding fluid. The urine oligosaccharides are composed by sialyl-oligosaccharides with equal numbers of alpha (2--6) and alpha (2--3) neuraminic acid -beta-galactoside bonds. A defect in the alpha (2--6) and alpha (2--3) neuraminidase activity in leucocytes and fibroblasts has been demonstrated. This deficit is the primary abnormality in I cell disease and it can be compared to the partial enzyme deficiencies described particularly in Mucolipidosis type I.