Amyloid Deposits in Skeletal Muscle: Long COVID and PEM

By SWA

Amyloid Deposits in Skeletal Muscle: Associated Illnesses and Conditions

Amyloid deposits in skeletal muscle can be associated with various illnesses and conditions, each impacting muscle function and leading to a range of symptoms. The specific type of amyloidosis and its underlying cause will determine the related illness. Here are some illnesses and conditions associated with amyloid deposits in skeletal muscle:

AL Amyloidosis (Immunoglobulin Light Chain Amyloidosis)

AL amyloidosis is a primary amyloidosis caused by the abnormal production of immunoglobulin light chains by plasma cells in the bone marrow. These light chains can deposit in various tissues, including skeletal muscle, leading to muscle weakness, pain, and dysfunction. This condition often presents with symptoms like fatigue, weight loss, and organ dysfunction, emphasizing the need for early diagnosis and treatment .

ATTR Amyloidosis (Transthyretin Amyloidosis)

ATTR amyloidosis can affect skeletal muscle, particularly in certain forms of the disease, such as hereditary ATTR amyloidosis with polyneuropathy. In this condition, mutated transthyretin protein forms amyloid deposits in nerves and muscle tissues, causing muscle weakness and peripheral neuropathy. This hereditary form typically presents in middle age and can also affect the heart and autonomic nervous system .

Systemic Amyloidosis

Systemic amyloidosis involves multiple organs and tissues, including skeletal muscle. Depending on the specific type of systemic amyloidosis (e.g., AA amyloidosis or others), skeletal muscle symptoms may vary, leading to generalized muscle weakness and discomfort. AA amyloidosis, often secondary to chronic inflammatory conditions, results in amyloid deposits derived from serum amyloid A protein .

Inflammatory Myopathies

In some cases, amyloid deposits can be found in skeletal muscles as part of inflammatory myopathies, such as inclusion body myositis (IBM). These conditions involve muscle inflammation and degeneration along with amyloid deposition, resulting in progressive muscle weakness. IBM, for example, typically affects older adults and can lead to significant disability .

Local Amyloidosis

Localized amyloidosis, though rare, can affect skeletal muscle. In localized amyloidosis, amyloid deposits are confined to a specific area or organ, potentially causing localized muscle symptoms or discomfort. This form of amyloidosis does not typically progress to systemic involvement but can be problematic in the affected area .

Secondary Amyloidosis

Secondary amyloidosis, often associated with chronic inflammatory diseases, can lead to amyloid deposits in various tissues, including skeletal muscle. Underlying conditions such as rheumatoid arthritis, chronic infections, or inflammatory disorders may contribute to muscle involvement. Effective management of the underlying condition is crucial to prevent or mitigate amyloid deposition .

Diagnosis and Evaluation

Diagnosing the specific related illness associated with amyloid deposits in skeletal muscle requires a thorough medical evaluation. This includes clinical assessments, imaging studies, and possibly a muscle biopsy to confirm the presence of amyloid. Blood tests, genetic testing, and evaluations of other organ systems may also be necessary to determine the type and extent of amyloidosis and to guide appropriate treatment strategies .

Conclusion

Amyloid deposits in skeletal muscle are a hallmark of several systemic and localized conditions, each requiring a tailored approach for diagnosis and management. Understanding the specific type of amyloidosis and its underlying cause is crucial for effective treatment and improving patient outcomes.

References

  1. Gertz, M.A., & Kyle, R.A. (1996). Primary systemic amyloidosis—a diagnostic primer. Mayo Clinic Proceedings, 71(6), 553-560.
  2. Merlini, G., & Bellotti, V. (2003). Molecular mechanisms of amyloidosis. New England Journal of Medicine, 349(6), 583-596.
  3. Benson, M.D., et al. (2018). Hereditary transthyretin amyloidosis: update on the genetic basis and treatment. Current Opinion in Gastroenterology, 34(3), 193-197.
  4. Adams, D., et al. (2017). Efficacy and safety of patisiran for familial amyloid polyneuropathy: a phase II multi-dose study. Orphanet Journal of Rare Diseases, 12(1), 1-12.
  5. Lachmann, H.J., et al. (2007). Natural history and outcome in systemic AA amyloidosis. New England Journal of Medicine, 356(23), 2361-2371.
  6. Gillmore, J.D., et al. (2011). Guidelines for the diagnosis and management of amyloidosis. British Journal of Haematology, 154(2), 232-245.
  7. Needham, M., & Mastaglia, F.L. (2007). Inclusion body myositis: current pathogenetic concepts and diagnostic and therapeutic approaches. The Lancet Neurology, 6(7), 620-631.
  8. Askanas, V., & Engel, W.K. (2006). Inclusion-body myositis: muscle-fiber molecular pathology and possible pathogenic significance of its similarity to Alzheimer's and Parkinson's disease brains. Acta Neuropathologica, 111(6), 535-549.
  9. Gertz, M.A. (2004). Managing localized amyloidosis. Leukemia Research, 28(9), 935-936.
  10. Wechalekar, A.D., et al. (2016). Systemic amyloidosis. The Lancet, 387(10038), 2641-2654.
  11. Husby, G. (1994). Amyloidosis and rheumatoid arthritis. Clinical and Experimental Rheumatology, 12(Suppl 10), S23-S26.
  12. Westermark, P., et al. (2007). A primer of amyloid nomenclature. Amyloid, 14(3), 179-183.
  13. Falk, R.H., & Comenzo, R.L. (1997). The systemic amyloidoses: advances in diagnosis and treatment. New England Journal of Medicine, 337(13), 898-909.

Note: By reading my blog, you acknowledge that I do not provide medical diagnoses or treatments. The information provided is meant to answer frequently asked questions and is gathered from reputable scientific papers.

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