Mycobacterium Fortuitum Differential Diagnoses

Updated: Nov 18, 2019
  • Author: Sami M Akram, MD, MHA, RDMS, FASA, FASN; Chief Editor: Pranatharthi Haran Chandrasekar, MBBS, MD  more...
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Diagnostic Considerations

Specimens from suspected infection sites (eg, sputum, bronchial wash, skin biopsy) should be sent to the laboratory for histopathology or cytopathology, AFB staining, and mycobacterial culture. Species-specific diagnosis is necessary, as antibiotic therapy must be guided by sensitivity and minimum inhibitory concentration (MIC).

Clinically, the differential diagnoses include other organisms that can cause chronic cutaneous, pulmonary, and deep-seated infections. The history of trauma is important in the pathogenesis of M fortuitum infections. Often, cervical adenitis is treated empirically with antituberculous medications in endemic areas, although M fortuitum infection rarely causes cervical lymphadenitis. [14]

Endemic fungal infection such as histoplasmosis, blastomycosis, and coccidioidomycosis can manifest as cutaneous lesions. However, such fungal cutaneous lesions frequently occur in immunocompromised individuals as a component of disseminated disease and without a history of trauma. [15]

Nocardia infections can cause cutaneous and chronic pulmonary manifestations in both immunocompromised and immunocompetent individuals. [16] Pulmonary infections in immunocompetent patients with structural lung disease have been reported. [17]

Microbiologically, M fortuitum infection must be differentiated from other members of its group, such as M abscessus, M chelonae, and M peregrinum. This is important, as antibiotic sensitivities may vary.

Deeper infections may lead to development of fistulae, in which case Actinomyces infections may also be included in the differential diagnoses.

Nodular skin lesions in the upper extremity that progressively worsen may resemble sporotrichosis.

Furunculosis may result from multiple bacterial and mycobacterial agents. Inquire about a history of exposure to a hot tub, nail salon procedure, or tattoo procedure.

Differential Diagnoses