AB124. Mucolipidosis type II: clinical features and laboratories

Abstract

Background

I-cell disease (Mucolipidosis II) is a rare lysosomal storage disorder caused by the deficiency of N-acetylglucosamine-l-phosphotransferase, an enzyme that transfers phosphate groups onto oligosaccharide units of lysosomal enzyme precursors. Due to the absence of transferase activity, the common phosphomannose recognition marker of acid hydrolases is not generated, and the enzymes are not targeted to the lysosomes I. As a consequence the enzymes are secreted into the extracellular space, and high activities can be found in the serum, cerebrospinal fluid and urine of the patients, whereas inside the cells (fibroblasts) the enzyme levels are considerably reduced. Mucolipidosis is also known as I-cell disease because of the coarse granular cytoplasmic inclusions seen in cultured skin fibroblasts which are large lysosomes containing heterogeneous material.

Objective

To describe clinical features and enzyme activity of patients with mucolipidosis type II.

Methods

Clinical features, laboratory and plasma lysosom enzyme activity by four MU-Fluorometric assay was study.

Results and conclusions

Sixteen cases (seven girls and nine boys) onset at 5.93±4.28 years of age the onset age of 2.3±3.1 years (median 1.25) with the feature of joint stiffness and bone deformation. 100% cases admitted with the feature of joint stiffness, chest deformation and kyphoscoliosis, 93.3% coarse facial features. No patients had hepatosplenomegaly on ultrasound, 5/15 patients had heart valves disease. Enzyme assay showed α-Hexosaminidase of 1,885.98±338.7 nmoL/mg plasma/17 h, α-Iduronate sulfatase of 4,534.78±1,062.97 nmoL/mg plasma/4 h. Mucolipidosis has seriously affected the life of the patients.