Dermatologic Manifestations of Nocardiosis Differential Diagnoses

Updated: Dec 09, 2016
  • Author: Brent A Shook, MD; Chief Editor: Dirk M Elston, MD  more...
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DDx

Diagnostic Considerations

Superficial skin infection: Streptococcal and staphylococcal infections are more common than nocardial infections. Maintain a high index of suspicion to diagnose infections with nocardial etiology. Notify the laboratory in advance when nocardiosis is suspected so that cultures are grown for longer than 48 hours.

Lymphocutaneous syndrome: Sporothrix schenckii is the most common cause. A dimorphic fungus causes sporotrichosis infection, and appropriate therapy includes excision, itraconazole, potassium iodide, or amphotericin B. When sophisticated culture techniques are unavailable, nocardiosis and sporotrichosis may be differentiated based on treatment response (nocardial lymphocutaneous syndrome also can be treated effectively with potassium iodide). Sporotrichosis typically follows a more indolent course and has a less inflammatory response compared with nocardiosis, although it also can be purulent.

Other less common causes of lymphocutaneous disease: These may be caused by non-Sporothrix fungi, such as Blastomyces, Coccidioides, Histoplasma, and Cryptococcus; bacteria, such as Francisella tularensis (tularemia), Staphylococcus aureus, and Streptococcus pyogenes; and viruses, such as herpes simplex and cowpox virus.

Mycobacterium marinum and other atypical mycobacteria: Along with Nocardia, M marinum is the most frequent cause of non-Sporothrix lymphocutaneous syndrome in the United States. Recent exposure to fresh- or salt-water sources (eg, fish tanks) provides an important historic clue. Treatment includes minocycline, trimethoprim-sulfamethoxazole (TMP-SMZ), and rifampin and ethambutol.

Leishmania brasiliensis: Infection is rare in the United States, but it is a relatively common cause of lymphocutaneous syndrome in the Middle East, Africa, Asia, and Latin America.

Mycetoma: The clinical presentation of mycetoma is distinctive. Determine the causative organism because treatment varies according to the infectious agent.

Differential Diagnoses