I-cell disease (mucolipidosis II):a report on its pathology.

The single most characteristic morphological feature in I-cell disease (ICD) is the accumulation of membrane-bound vacuoles in mesenchymal cells (mainly fibroblasts). No true storage can be documented in those vacuoles. That their contents could have been dissolved during fixation or embedding remains however a possibility. Remnants consisting of a few lamellar arrays and of small amounts of fibrillo-granular material are too scarce for histochemical characterization. In hepatocytes large cells in the white pulp of the spleen and in myocardial fibers, vacuoles with fixative insoluble contents have been discovered; they are nowhere very abundant and their specificity is questionable. Because the affected fibroblastic elements represent a small fraction in any organ, most secondary biochemical abnormalities are expected to be detectable only in purely fibroblastic tissues. Our pathological study contributes to the understanding of some of the clinical features characteristic of ICD and stresses major morphological differences between ICD and the many diseases classified as mucopolysaccharidoses and mucolipidoses.