Primary cutaneous tuberculosis

Primary cutaneous tuberculosis is a rare form of extrapulmonary tuberculosis in which Mycobacterium tuberculosis (or occasionally M. bovis) directly inoculates the skin as the initial site of infection in a person without prior immunity to tuberculosis. This condition is also known as tuberculous chancre or tuberculosis cutis primaria. It occurs when the mycobacterium enters through a break in the skin — such as an abrasion, wound, or mucous membrane — in an individual who has not been previously sensitized to tuberculosis. The skin is the primary organ system affected, though regional lymph nodes frequently become involved, forming a complex analogous to the Ghon complex seen in pulmonary tuberculosis. Clinically, primary cutaneous tuberculosis typically presents as a painless, firm papule or nodule at the inoculation site that may gradually enlarge and ulcerate over several weeks. The lesion is often accompanied by painless regional lymphadenopathy. Common sites include exposed areas such as the face, hands, and lower extremities, as well as mucous membranes. The tuberculin skin test is initially negative but converts to positive within several weeks as the immune response develops. In immunocompetent individuals, the lesion may heal spontaneously with scarring, but in immunocompromised patients, dissemination can occur. Treatment follows standard anti-tuberculosis chemotherapy regimens, typically involving a combination of isoniazid, rifampicin, pyrazinamide, and ethambutol during an initial intensive phase, followed by a continuation phase with isoniazid and rifampicin. The total duration of treatment is generally six to nine months. Early diagnosis through skin biopsy, culture, and molecular testing (such as PCR) is important to prevent complications including lymphatic spread or secondary dissemination. Prognosis is generally favorable with appropriate and timely anti-tuberculosis therapy.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

Common questions about Primary cutaneous tuberculosis