A 43-Year-Old Woman with a New Ulcer on One Hand

Differential Diagnosis

• Mycobacterium chelonae infection
• Mycobacterium marinum infection
• Cutaneous phaeohyphomycosis infection
• Foreign body granuloma

Diagnosis

This is Myobacterium marinum infection. M marinum is an atypical mycobacterial skin infection contracted from contaminated fish tanks, swimming pools, lake water and salt water. Minor trauma is a predisposing factor.

Men are affected more commonly than women.

Learnings/What to Look for

• The typical skin lesion consists of a pustule or nodule and develops 2–3 weeks after exposure
• Nodules may ulcerate, suppurate, and spread via lymphangitic spread (about 25% of cases)
• In more severe infections, deeper manifestations such as tenosynovitis, arthritis, bursitis, or osteomyelitis may be seen
• In immunosuppressed patients, disease can disseminate to the lungs or other systems; bacteremia is rare
  

Pearls for Urgent Care Management

• Infection is usually mild and self-limited, with lesions healing over 1 to 2 years if left untreated
• Treatments found to expedite healing include minocycline, clarithromycin, doxycycline, and trimethoprim-sulfamethoxazole
• While M marinum is naturally multidrug-resistant, drug resistance varies. As such, combination therapy may be required
• Cryotherapy, x-ray therapy, electrodesiccation, photodynamic therapy, and local hyperthermic therapy have also been reported to be effective

Acknowledgment: Image and case presented by VisualDx (www.VisualDx.com/jucm).