Cutaneous Nocardiosis
Nocardia species are soil bacteria found worldwide. Disease in humans is rare, and often signals significant immune deficiency. Human infection usually occurs through inhalation, and rarely through direct cutaneous inoculation. In about 50% of cases of inhalational Nocarida bacteria can disseminate particularly to the central nervous system and subcutaneous tissues. The extent of the infection is determined by the immune status of the host.
Four clinical types of cutaneous nocardiosis are recognized: mycetoma, lymphocutaneous infection, superficial skin infection, and secondary skin infection associated with disseminated disease.
Hematogenous dissemination to the skin, in the form of cellulitis, nodules, or abscesses, probably occurs more often than primary infection of the skin. Primary cutaneous infection may follow skin injury from thorns, insect bites, and even cat scratches. Localized cutaneous infections may present as chronically draining ulcerative lesions, a slowly expanding nodule, or rarely, pustules, abscesses, cellulitis, or pyoderma. In one-third of individuals, the infection can spread to involve the regional lymph nodes, producing a syndrome similar to that of sporotrichosis, known as the lymphocutaneous syndrome. The draining lymphatics become inflamed and swollen and a chain of secondary nodules develops along the course of the lymphatics. These may break down and ulcerate.
Differential Diagnosis: Cutaneous nocardiosis can be distinguished from cutaneous anthrax in the following manner.
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Cutaneous norcardiosis |
Cutaneous anthrax |
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*Pulmonary nodules and skin lesions are present with lymphadenopathy in immunosuppressed patient *Primary lesion is associated with nodular, tender lymphatic chain to regional lymph node |
* Ulcer with eschar painless * Ulcer and eschar are surrounded by characteristic non-pitting edema |
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