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Mucolipidosis II. The clinical, radiological and biochemical features in three cases
Insights
Mucolipidosis II (I-Cell Disease) presents with severe developmental delays and distinct physical features in infants. Diagnosis involves characteristic cellular and biochemical findings in fibroblasts, crucial for understanding this rare lysosomal storage disorder.
Area of Science:
- Biochemistry
- Genetics
- Pediatrics
Background:
- Mucolipidosis II (ML II), also known as I-Cell Disease, is a severe lysosomal storage disorder.
- It is characterized by the accumulation of undegraded glycosaminoglycans and glycoproteins within lysosomes.
- ML II results from a deficiency in the enzyme N-acetylglucosamine-1-phosphotransferase, leading to improper targeting of lysosomal enzymes.
Purpose of the Study:
- To describe the clinical, radiological, and biochemical characteristics of Mucolipidosis II in three infants.
- To highlight the diagnostic features of ML II, including cellular and enzymatic abnormalities.
- To emphasize the importance of early diagnosis for patient management.
Main Methods:
- Clinical observation and assessment of three infants with suspected ML II.
- Radiological imaging to evaluate skeletal abnormalities.
- Cytological examination of skin fibroblasts for lysosomal inclusions.
- Biochemical assays of lysosomal enzyme activities in cultured skin fibroblasts and plasma.
Main Results:
- Infants presented with severe psychomotor delay, failure to thrive, coarse facial features, gingival hyperplasia, joint stiffness, inguinal hernia, and skin induration.
- Radiological findings were characteristic but not specific for ML II.
- Skin fibroblasts showed typical lysosomal inclusions (I-cells).
- Deficient activity of arylsulphatase A and B, and hexosaminidase A and B was observed in fibroblasts, with marked increases in plasma and culture medium.
Conclusions:
- The study confirms the characteristic clinical, radiological, and biochemical phenotype of Mucolipidosis II in affected infants.
- Cytological and biochemical analyses of skin fibroblasts are crucial for diagnosing ML II.
- Early identification of ML II is essential for appropriate clinical care and genetic counseling.
Abstract:
We report on the clinical, radiological and biochemical features of mucolipidosis II in three infants. One with subtle phenotypical findings died at 2 weeks of age without a specific diagnosis. A sibling who died at 2 years of age and another infant, presently 3.5 years of age manifest all the characteristic features of mucolipidosis II: extreme psychomotor delay and failure to thrive, coarse facial features, gingival hyperplasia, joint stiffness, inguinal hernia and skin induration. The corneae were normal and there was no mucopolysacchariduria. Radiologically, these infants show changes which are characteristic but not specific for mucolipidosis II. Cytologically, skin fibroblasts from these patients demonstrate the lysosomal inclusions typical of I-Cell Disease. Biochemically, cultured skin fibroblasts show deficient activity of arylsulphatase A and B and hexosaminidase A and B. These acid hydrolases were increased markedly in plasma and in the culture medium of the skin fibroblasts.