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Key Features

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Essentials of Diagnosis
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  • Chronic unilateral cervical lymphadenitis

  • Granulomas of the skin

  • Chronic bone lesion with draining sinus (chronic osteomyelitis)

  • Tuberculin skin test (TST) of 5–8 mm, negative chest radiograph, and negative history of contact with tuberculosis

  • Diagnosis by positive culture

  • Disseminated infection in patients with AIDS

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General Considerations
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  • More than 130 species of acid-fast mycobacteria other than M tuberculosis may cause subclinical infections and occasionally clinical disease resembling tuberculosis

  • Strains of nontuberculous mycobacteria (NTM) are common in soil, food, and water

  • Organisms enter the host by small abrasions in skin, oral mucosa, or gastrointestinal mucosa

  • Mycobacterium avium complex (MAC), Mycobacterium kansasii, Mycobacterium fortuitum, Mycobacterium abscessus, Mycobacterium marinum, and Mycobacterium chelonae are most commonly encountered

  • M fortuitum, M abscessus, and M chelonae are "rapid growers" requiring 3–7 days for recovery, whereas other mycobacteria require several weeks

  • After inoculation, they form colonies closely resembling M tuberculosis morphologically

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Clinical Findings

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  • Lymphadenitis

    • MAC is the most common organism

    • A submandibular or cervical node swells slowly and is firm and initially somewhat tender

    • Low-grade fever may occur

    • Over time, the node may suppurate and drain chronically

    • Nodes in other areas of the head and neck and elsewhere are sometimes involved

    • Chronic intermittent drainage is common, but in many cases healing occurs after 4–12 months

  • Pulmonary disease

    • In the western United States, usually due to M kansasii or MAC

    • In the eastern United States and in other countries, usually caused by MAC

    • Presentation is clinically indistinguishable from that of tuberculosis

    • Adolescents with cystic fibrosis may be infected with nontuberculous mycobacteria with resulting fever and declining pulmonary function

  • Swimming pool granuloma

    • Commonly due to M marinum

    • A solitary chronic granulomatous lesion with satellite lesions develops after minor trauma in infected swimming pools or other aquatic sources

    • Minor trauma during exposure to home aquariums or other aquatic environments may also lead to infection

  • Chronic osteomyelitis

    • Caused by MAC, M kansasii, M fortuitum, or other rapid growers

    • Swelling and pain over a distal extremity, radiolucent defects in bone, fever, and clinical and radiographic evidence of bronchopneumonia are present

    • Cases are rare

  • Meningitis

    • Caused by M kansasii

    • May be indistinguishable from tuberculous meningitis

  • Disseminated infection

    • Children are ill, with fever and hepatosplenomegaly, and organisms are demonstrated in bone lesions, lymph nodes, or liver

    • Between 60% and 80% of patients with AIDS acquired MAC infection in the past, characterized by fever, night sweats, weight loss, and diarrhea

    • Infection usually indicates severe immune dysfunction and is associated with CD4 lymphocyte counts less than 50/μL

    • Infection is very rare due to more effective HIV therapy

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Diagnosis

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Laboratory Findings
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  • Mantoux testing

    • Negative or small reaction (< 10 mm) in most cases

    • Larger reactions may be seen particularly with M marinum infection

  • Interferon-gamma release assay (IGRA) tests are commonly negative although M marinum, M kansasii, and M szulgai may cause ...

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