A case of mucolipidosis II presenting with prenatal skeletal dysplasia and severe secondary hyperparathyroidism at birth

Heo, Ju Sun; Choi, Ka Young; Sohn, Se Hyoung; Kim, Curie; Kim, Yoon Joo; Shin, Seung Han; Lee, Jae Myung; Lee, Juyoung; Sohn, Jin A; Lim, Byung Chan; Lee, Jin A; Choi, Chang Won; Kim, Ee-Kyung; Kim, Han-Suk; Kim, Beyong Il; Choi, Jung-Hwan

phosphotransfer-ase) 1) . This enzyme is involved in the first step of synthesis of the mannose 6-phosphate signal, which allows specific targeting of lysosomal acid hydrolase from the trans-Golgi network to lysosomes [2] [3] [4] . The lack of this enzyme precludes the generation of the common phosphomannosyl recognition marker of lysosomal enzymes 1, [5] [6] [7] [8] [9] [10] . Consequently, newly synthesized lysosomal enzymes are secreted into the extracellular space rather than targeted to the lysosomes. Thus, affected lysosomes are secondarily deficient in most acid hydrolases 11) and are unable to degrade some macromolecules. In contrast, plasma levels of lysosomal hydrolases are high 12) . The resulting lysosomal storage, which was first reported in cultured fibroblasts 13, 14) , is seen as cytoplasmic inclusion bodies, particularly in mesenchymal cells, hence the term I-cell disease 12, 15) .