[I-cell disease and pseudo-Hurler polydystrophy]

I-cell disease (ML II) and pseudo-Hurler poly-dystrophy (ML-III) are lysosomal storage diseases caused by abnormal lysosomal enzyme phosphorylation and localization. In both diseases, newly synthesized lysosomal enzymes are secreted into the extra-cellular medium instead of being targeted correctly to lysosomes. All cells and tissues of affected medium instead of being targeted correctly to lysosomes. All cells and tissues of affected patients are deficient in UDP-N-acetylglucosamine: lysosomal enzyme N-acetylglucosamine-1-phosphotransferase activity. However, we have demonstrated that liver cells from ML II patients have normal lysosomal enzyme contents. In Japan, ML II is a relatively common disorder whereas ML III is very rare as compared to Western Countries. The natural history of 21 cases with ML II, as well as 5 prenatally diagnosed cases of ML II, have been reported by our research group.