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Mannosidosis: two brothers with different degrees of disease severity
Abstract:
Two siblings with different degrees of mental retardation, skeletal dysplasia, coarse facies, delayed speech, motor incoordination, recurrent respiratory infections, and immunological abnormalities, were found to have deficient alpha-mannosidase activity. Cultured skin fibroblasts in one sib were markedly deficient in alpha-mannosidase while all other lysosomal enzymes tested were within the normal range. The more severely affected sib came to autopsy and was found to have "washed-out" appearing cortical neurons and marked histiocytosis effacing lymph node architecture and partially replacing the bone marrow. The post-mortem brain and liver samples demonstrated a deficiency in alpha-mannosidase relative to the elevations of other lysosomal enzymes. Although the patterns of abnormalities in the two cases closely match those of descriptions of "type II" and "type I" mannosidosis respectively, the variation should be due to genetic modifiers or environmental effects since the brothers must have shared similar alpha-mannosidase mutations. Immunologic abnormalities present in the more severely affected sib suggest that the differential survival seen in mannosidosis types I and II may be due to differences in their immune systems.
Insights
Two siblings with alpha-mannosidase deficiency exhibited varying symptoms of mannosidosis. Genetic or environmental factors likely explain the differing disease severity, potentially linked to immune system variations.
Area of Science:
- Biochemistry
- Genetics
- Immunology
Background:
- Mannosidosis is a rare lysosomal storage disorder.
- Deficiency in alpha-mannosidase enzyme activity causes mannosidosis.
- Clinical presentation varies, with Type I and Type II described.
Observation:
- Two siblings presented with distinct clinical features of mannosidosis, including mental retardation, skeletal dysplasia, and immune deficiencies.
- Fibroblast studies revealed deficient alpha-mannosidase activity in one sibling, with other lysosomal enzymes remaining normal.
- Autopsy findings in the more severely affected sibling showed neuronal loss and histiocytosis, with enzyme assays confirming alpha-mannosidase deficiency in brain and liver.
Findings:
- The siblings' differing clinical manifestations, despite likely shared alpha-mannosidase mutations, suggest the influence of genetic modifiers or environmental factors.
- Immunological abnormalities were noted in the more severely affected sibling, potentially impacting disease progression and survival.
- The study highlights the complex interplay between enzyme deficiency, genetic background, and immune function in mannosidosis.
Implications:
- Understanding the factors contributing to symptom variability is crucial for accurate diagnosis and prognosis of mannosidosis.
- Further research into genetic modifiers and immune system involvement could reveal therapeutic targets.
- This case study underscores the importance of comprehensive enzymatic and immunological assessments in lysosomal storage disorders.