M.marinum infection mimicking sporotrichosis

Eruptions in a patient with Crohn’s disease using infliximab:


Culture revealed M.marinum, with positive IGRA (results were negative previously)

Mycobacterium marinum

  • Oppoturnistic bacteria that causes aquarium granuloma (affects individuals who work with fish or have aquarium at home).
  • Most are acquired during the handling of the aquariums such as cleaning or changing the water.
  • Typically affects hands, but can also affect knees and legs in swimming pool related cases.
  • Commonly happened in immunosuppressed patients
    – TNF-a inhibitors suppress cellular immunity.
  • Commonly misdiagnosed. Can mimic sporotrichosis by evolving into ascending lymphangitis.
  • Rx: takes a long time; treatment should be continued 1-2 months after resolution of symptoms (=3-4 months in total)
    – 2 antibiotics needed: clarithromycin + ethambutol; rifampin can be added if there is deep tissues involvement
    – Also sensitive to doxycycline, ciprofloxacin and sulfonamides.
    – Resistance to isoniazid and pyrazinamide.

Learning point

  • The use of TNF-α inhibitors is widespread, and the presence of sporotrichoid eruptions in these patients should suggest the possibility of mycobacterial infection.


  1. Jessica Kim So, M.D., and Taraneh Paravar, M.D. Sporotrichoid Mycobacterial Infection. N Engl J Med 2015; 373:1761
  2. http://emedicine.medscape.com/article/223363-overview

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