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Fatal reducing body myopathy. Ultrastructural and immunohistochemical observations
B H Kiyomoto1, N Murakami, Y Kobayashi
1Department of Ultrastructural Research, National Institute of Neuroscience, NCNP, Tokyo, Japan.
Insights
This study describes two infant cases of rapidly progressive muscle weakness and hypotonia. The key finding was the presence of numerous reducing bodies (RB) in degenerating muscle fibers, possibly linked to nuclear degeneration.
Area of Science:
- Neurology
- Pediatrics
- Muscle Biology
Background:
- Investigating rare pediatric neuromuscular disorders.
- Understanding the pathology of progressive muscle weakness in infants.
Observation:
- Two female infants presented with normal early development followed by progressive hypotonia and weakness.
- Rapid disease progression led to respiratory failure and death in both cases before age 5.
Findings:
- Muscle biopsies revealed mild inflammation and numerous reducing bodies (RB) in degenerating muscle fibers.
- Electron microscopy showed RBs as granular material near degenerating nuclei.
- RBs lacked reactivity to antibodies for structural proteins, cytoskeletal proteins, and nuclear components, but showed occasional ubiquitin staining.
Implications:
- The origin of reducing bodies remains unclear but may indicate primary nuclear degeneration.
- These findings contribute to the understanding of unique pathological markers in severe pediatric myopathies.
- Further research is needed to elucidate the precise role and origin of reducing bodies in myofibrillar degeneration.
Abstract:
Two female infants who developed normally during infancy began to have progressive muscle hypotonia and weakness from 2 years 10 months and 2 years 3 months of ages, respectively. Both patients had rapidly progressive muscle weakness with death from respiratory failure at 4 years 11 months and 3 years 9 months, respectively. In addition to mild inflammation in their muscle biopsies, the most striking finding was the presence of numerous reducing bodies (RB) in almost all degenerating fibers. By electron microscopy, these bodies consisted of fine granular material, usually located around the degenerating nucleus. These bodies showed no immunohistochemical reaction to antibodies against structural, cytoskeletal and membrane proteins and a histone-specific antibody against nuclei and chromosomes. They were occasionally positively stained with a ubiquitin antibody. Although the origin of these bodies remains unknown, they appeared to be related to active myofibrillar degeneration, probably resulting from primary nuclear degeneration.