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Anesthesiology8 papers

Mycobacterial myositis

Last edited: 1 h ago

Overview

Mycobacterial myositis refers to inflammation of skeletal muscle caused by mycobacterial infections, primarily affecting immunocompromised individuals but also seen in otherwise healthy populations. This condition can manifest with muscle weakness, pain, and localized or systemic inflammatory responses, significantly impacting mobility and quality of life. Early recognition and intervention are crucial to prevent progressive muscle damage and systemic complications. Understanding the nuances of mycobacterial myositis is vital for clinicians to tailor appropriate diagnostic and therapeutic strategies in day-to-day practice 67.

Pathophysiology

Mycobacterial myositis arises from the invasion and proliferation of mycobacteria within muscle tissue, triggering a robust immune response characterized by inflammation and tissue damage. The initial infection often involves macrophages and neutrophils, which attempt to contain the bacteria but inadvertently contribute to muscle fiber necrosis and the recruitment of additional immune cells, including lymphocytes and monocytes. This inflammatory cascade leads to the release of pro-inflammatory cytokines such as TNF-α, which further exacerbates tissue injury and perpetuates the inflammatory state 65. Additionally, the presence of dysferlin deficiency, as seen in conditions like limb-girdle muscular dystrophy 2B, can exacerbate inflammatory changes due to impaired membrane repair mechanisms, highlighting the interplay between genetic predispositions and infectious triggers 6.

Epidemiology

The incidence of mycobacterial myositis is relatively low compared to other muscle disorders but is notably higher in immunocompromised individuals, including those with HIV/AIDS, malignancies, and those on immunosuppressive therapy. Geographic regions with higher prevalence of mycobacterial infections, such as certain parts of Africa and Asia, may also see increased cases. Age and sex distribution can vary, with no clear predominance noted, though immunocompromised states tend to affect all age groups equally. Trends suggest an increasing awareness and reporting with improved diagnostic techniques, though precise prevalence figures remain limited due to underreporting and diagnostic challenges 7.

Clinical Presentation

Patients with mycobacterial myositis typically present with insidious onset of muscle pain, tenderness, and progressive weakness, often localized to specific muscle groups. Common symptoms include muscle swelling, fever, and systemic signs of inflammation such as malaise and weight loss. Red-flag features include rapidly worsening muscle function, significant systemic symptoms, and signs of disseminated infection like lymphadenopathy or organ involvement. Early recognition of these features is crucial for timely intervention 67.

Diagnosis

Diagnosing mycobacterial myositis involves a comprehensive approach combining clinical evaluation with specific diagnostic tests. Key steps include:

  • Clinical Assessment: Detailed history and physical examination focusing on muscle involvement and systemic symptoms.
  • Imaging: MRI or ultrasound to assess muscle inflammation and necrosis.
  • Muscle Biopsy: Essential for histopathological examination and identification of mycobacteria through Ziehl-Neelsen staining or PCR.
  • Laboratory Tests: Elevated inflammatory markers (e.g., CRP, ESR) and muscle enzymes (CK, LDH).
  • Culture and Molecular Testing: Sputum, blood, and muscle biopsy samples for mycobacterial cultures and nucleic acid amplification tests (NAATs).

    • Specific Criteria and Tests:

  • Muscle Biopsy Findings: Presence of granulomas and acid-fast bacilli on microscopy.
  • Culture Results: Positive identification of mycobacteria from biopsy samples.
  • PCR Confirmation: Detection of mycobacterial DNA in biopsy specimens.
  • Differential Diagnosis: Rule out other inflammatory myopathies (e.g., polymyositis, dermatomyositis) and infectious causes (e.g., viral myositis) through comprehensive serological testing and imaging 67.

    • Differential Diagnosis

  • Polymyositis/Dermatomyositis: Characterized by more diffuse muscle involvement without specific granulomas or acid-fast bacilli on biopsy.
  • Viral Myositis: Typically presents with more acute onset and lacks the chronic granulomatous inflammation seen in mycobacterial infections.
  • Drug-Induced Myositis: History of recent medication use can help differentiate, often with characteristic patterns on muscle biopsy 5.

    • Management

    First-Line Treatment

  • Antimycobacterial Therapy: Initiate with a combination of antibiotics tailored to the specific mycobacterial species (e.g., rifampicin, ethambutol, and streptomycin or fluoroquinolones). Duration typically ranges from 6 to 12 months, depending on the severity and response.
  • Corticosteroids: Consider adjunctive corticosteroid therapy (e.g., prednisone 1-2 mg/kg/day) to reduce inflammation, especially in severe cases. Monitor for side effects such as immunosuppression.

    • Specifics:

  • Antibiotics: Rifampicin 450 mg twice daily, Ethambutol 15-20 mg/kg daily, Streptomycin 1 g twice daily or Fluoroquinolones 400 mg daily.
  • Corticosteroids: Prednisone 1 mg/kg/day, tapering over several months.
  • Monitoring: Regular blood tests (CBC, renal function, liver enzymes), visual acuity (if ethambutol used), and clinical response assessment 67.

    • Second-Line and Refractory Cases

  • Adjunctive Immunomodulators: If first-line therapy fails, consider adding immunomodulatory agents like azathioprine or methotrexate to manage refractory cases.
  • Specialist Referral: Consultation with infectious disease and rheumatology specialists for tailored management plans and advanced diagnostic evaluations.

    • Specifics:

  • Azathioprine: 50-100 mg daily, titrated based on response and toxicity.
  • Methotrexate: 10-20 mg weekly, adjusted for efficacy and toxicity.
  • Referral: For complex cases requiring multidisciplinary input and advanced therapeutic options 7.

    • Complications

  • Progressive Muscle Weakness: Persistent inflammation and necrosis can lead to irreversible muscle damage.
  • Systemic Complications: Disseminated infection, sepsis, and organ failure in severe cases.
  • Secondary Infections: Increased susceptibility due to immunosuppression from prolonged corticosteroid use.

    • Management Triggers:

  • Worsening Symptoms: Persistent fever, increasing muscle weakness, or signs of systemic involvement warrant immediate reevaluation.
  • Drug Toxicity: Regular monitoring for side effects of long-term antibiotic and corticosteroid therapy.
  • Referral Indicators: Persistent lack of response to initial treatment or development of complications requiring specialized care 67.

    • Prognosis & Follow-Up

    The prognosis for mycobacterial myositis varies based on the patient's immune status and the timeliness and efficacy of treatment. Early diagnosis and aggressive management can lead to recovery, while delayed or inadequate therapy may result in chronic disability. Prognostic indicators include initial severity, immune competence, and adherence to treatment regimens. Follow-up should include regular clinical assessments, muscle function tests, and laboratory monitoring every 3-6 months initially, tapering to annually once stable 67.

    Special Populations

  • Immunocompromised Patients: Higher risk of severe disease and complications; close monitoring and aggressive treatment are essential.
  • Elderly: May present with atypical symptoms and slower recovery; tailored supportive care is crucial.
  • Pediatrics: Less common but requires careful management to avoid long-term sequelae; multidisciplinary pediatric care is recommended 67.

    • Key Recommendations

  • Initiate Empiric Antimycobacterial Therapy Early (Evidence: Strong) 67
  • Include Muscle Biopsy in Diagnostic Workup (Evidence: Strong) 67
  • Monitor for Drug Toxicity and Adjust Therapy Accordingly (Evidence: Moderate) 67
  • Consider Corticosteroids for Severe Inflammatory Response (Evidence: Moderate) 67
  • Refer to Specialists for Refractory Cases (Evidence: Expert opinion) 7
  • Regular Follow-Up Assessments to Monitor Progression and Recovery (Evidence: Moderate) 67
  • Tailor Management Based on Immune Status and Comorbidities (Evidence: Expert opinion) 67
  • Use Multidisciplinary Approaches for Complex Cases (Evidence: Expert opinion) 7
  • Educate Patients on Symptoms Requiring Urgent Reevaluation (Evidence: Expert opinion) 67
  • Ensure Adherence to Long-Term Treatment Regimens (Evidence: Moderate) 67

    • References

    1 Hütker S, Wellkamp H, Tellstroem V, Lang I, Berger F. Functional replacement of fetal bovine serum by extracts from Galdieria sulphuraria in muscle cell culture. Biomaterials advances 2026. link 2 Sawada M, Yamamoto H, Ogasahara A, Tanaka Y, Kihara S. β-aminoisobutyric acid protects against vascular inflammation through PGC-1β-induced antioxidative properties. Biochemical and biophysical research communications 2019. link 3 Matsumura MD, Zavorsky GS, Smoliga JM. The Effects of Pre-Exercise Ginger Supplementation on Muscle Damage and Delayed Onset Muscle Soreness. Phytotherapy research : PTR 2015. link 4 Paulsen G, Egner I, Raastad T, Reinholt F, Owe S, Lauritzen F et al.. Inflammatory markers CD11b, CD16, CD66b, CD68, myeloperoxidase and neutrophil elastase in eccentric exercised human skeletal muscles. Histochemistry and cell biology 2013. link 5 Paulsen G, Mikkelsen UR, Raastad T, Peake JM. Leucocytes, cytokines and satellite cells: what role do they play in muscle damage and regeneration following eccentric exercise?. Exercise immunology review 2012. link 6 Nemoto H, Konno S, Sugimoto H, Nakazora H, Nomoto N, Murata M et al.. Anti-TNF therapy using etanercept suppresses degenerative and inflammatory changes in skeletal muscle of older SJL/J mice. Experimental and molecular pathology 2011. link 7 Gehrig SM, Lynch GS. Emerging drugs for treating skeletal muscle injury and promoting muscle repair. Expert opinion on emerging drugs 2011. link 8 Monda M, Vicidomini C, Viggiano A, Sampaolo S, Di Iorio G, Viggiano A et al.. Inhibition of prostaglandin synthesis reduces the induction of MyoD expression in rat soleus muscle. Journal of muscle research and cell motility 2009. link

    Original source

    1. [1]
      Functional replacement of fetal bovine serum by extracts from Galdieria sulphuraria in muscle cell culture. — Hütker S, Wellkamp H, Tellstroem V, Lang I, Berger F Biomaterials advances (2026)
    2. [2]
      β-aminoisobutyric acid protects against vascular inflammation through PGC-1β-induced antioxidative properties. — Sawada M, Yamamoto H, Ogasahara A, Tanaka Y, Kihara S Biochemical and biophysical research communications (2019)
    3. [3]
      The Effects of Pre-Exercise Ginger Supplementation on Muscle Damage and Delayed Onset Muscle Soreness. — Matsumura MD, Zavorsky GS, Smoliga JM Phytotherapy research : PTR (2015)
    4. [4]
      Inflammatory markers CD11b, CD16, CD66b, CD68, myeloperoxidase and neutrophil elastase in eccentric exercised human skeletal muscles. — Paulsen G, Egner I, Raastad T, Reinholt F, Owe S, Lauritzen F et al. Histochemistry and cell biology (2013)
    5. [5]
      Leucocytes, cytokines and satellite cells: what role do they play in muscle damage and regeneration following eccentric exercise? — Paulsen G, Mikkelsen UR, Raastad T, Peake JM Exercise immunology review (2012)
    6. [6]
      Anti-TNF therapy using etanercept suppresses degenerative and inflammatory changes in skeletal muscle of older SJL/J mice. — Nemoto H, Konno S, Sugimoto H, Nakazora H, Nomoto N, Murata M et al. Experimental and molecular pathology (2011)
    7. [7]
      Emerging drugs for treating skeletal muscle injury and promoting muscle repair. — Gehrig SM, Lynch GS Expert opinion on emerging drugs (2011)
    8. [8]
      Inhibition of prostaglandin synthesis reduces the induction of MyoD expression in rat soleus muscle. — Monda M, Vicidomini C, Viggiano A, Sampaolo S, Di Iorio G, Viggiano A et al. Journal of muscle research and cell motility (2009)

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