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Intranuclear and cytoplasmic filamentous inclusions in distal myopathy (Welander)
Abstract:
Ultrastructural examination of anterior tibial muscle from four patients with late-onset autosomal dominant distal myopathy of Welander-type revealed intrasarcoplasmic filamentous inclusions in association with rimmed vacuoles. In one of the patients, identical intranuclear filamentous inclusions were also found. These filamentous inclusions are similar to those described in inclusion body myositis (IBM). They have also been observed in hereditary neuromuscular disorders including autosomal recessive distal myopathy. Thus, the filamentous inclusions occur in different neuromuscular conditions with different etiologies. These findings further raise the question of the specificity of the filamentous inclusions in IBM.
Insights
Filamentous inclusions in Welander myopathy muscle resemble those in inclusion body myositis. These inclusions appear in various neuromuscular disorders, questioning their specificity for inclusion body myositis.
Area of Science:
- Neuromuscular Disorders
- Muscle Pathology
- Genetics
Background:
- Late-onset autosomal dominant distal myopathy (Welander-type) is a rare genetic neuromuscular disorder.
- Ultrastructural examination is crucial for diagnosing and understanding muscle diseases.
Observation:
- Ultrastructural analysis of anterior tibial muscle in four Welander-type myopathy patients was performed.
- Intrasarcoplasmic filamentous inclusions were observed in muscle fibers, often near rimmed vacuoles.
Findings:
- Identical filamentous inclusions were also found within the nucleus in one patient.
- These inclusions share ultrastructural similarities with those found in inclusion body myositis (IBM).
- Similar filamentous inclusions have been noted in other hereditary neuromuscular conditions, including autosomal recessive distal myopathy.
Implications:
- The presence of similar filamentous inclusions across different neuromuscular disorders suggests they are not specific to inclusion body myositis.
- This finding necessitates a re-evaluation of the diagnostic specificity of these inclusions in IBM.
- Further research is needed to elucidate the precise role and origin of these inclusions in various myopathies.