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Updated: May 16 2021

Atypical Mycobacterium Infections


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Images marinum.jpg
  • summary
    • Atypical Mycobacterial Infections of the hand are rare hand infections that are most commonly caused by M. marinum.
    • Diagnosis is made by clinical examination with presence papules, ulcers, and nodules and confirmed with cultures (Lowenstein-Jensen culture agar).
    • Treatment of early disease is oral antibiotics (antimycobacterials).
  • Epidemiology
    • Incidence
      • rare
        • 0.05 per 100,000 annually
    • Demographics
      • often found in marine workers
    • Location
      • hand and wrist are involved in 50% of cases
    • Risk factors
      • immunocompromised host
  • Etiology
    • Pathophysiology
      • incubation
        • average incubation period is two weeks, but can be up to six months
        • average time to diagnosis and appropriate treatment is more than 1 year
      • organisms
        • widely encountered in the environment, but rarely cause human pathology
          • M. marinum
            • most common atypical mycobacterium infection
            • more common in stagnant fresh or salt water (aquariums)
          • M kansasii
            • found in soil
          • M terrae
            • found in soil
          • M. avium intracellulare
            • most common in terminal AIDS patients, but can occur in non-HIV patients
  • Presentation
    • Symptoms
      • cutaneous rash with discomfort
    • Physical exam
      • papules, ulcers, and nodules are common, especially on the hands
        • many times presents with a single nodule that may ultimately spread to the lymph nodes
        • indistinguishable from tuberculous mycobacterial infection
  • Studies
    • Histology
      • granulomas may or may not demonstrate acid-fast bacilli on AFB stain
    • Cultures and sensitivities are key to diagnosis
      • Lowenstein-Jensen culture agar
        • M. marinum incubated specifically at 30 to 32° C
        • M. avium intracellulare incubated at room temperature
  • Differential
    • Herpetic Whitlow
    • Fungal infections
    • Psoriasis
  • Diagnosis
    • Clinical and culture-based
      • diagnosis is made with careful history and physical examination and confirmed with a positive cultures
  • Treatment
    • Nonoperative
      • oral antibiotics
        • indications
          • if diagnosed at early stage
        • medications
          • ethambutol, tetraycline, trimethoprim-sulfamethoxazole, clarithromycin, azithromycin
          • add rifampin if osteomyelitis present
    • Operative
      • surgical debridement + oral antibiotics in combination for 3 to 6 months
        • indications
          • later stage disease
        • use a combination of above medications
  • Prognosis
    • Natural history
      • early presentation includes papules, nodules, and ulcers
      • late presentation may have progressed to tenosynovitis, septic arthritis, or osteomyelitis
    • Morbidity & mortality
      • mortality rate with presence of sepsis is 32%
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