Later, due to the obliterative vascular changes, a wedge-shaped area of focal dermal necrosis develops, surrounded by a granulomatous inflammatory infiltrate with giant cells and epithelioid histiocytes. Well-formed tuberculoid granulomas with Langerhans giant cells are not typically present in the lesions. Special stains for mycobacteria are characteristically negative. The histologic differential diagnosis will depend on the timing of the biopsy. Inflammatory palisading granulomas such as granuloma annulare and infectious granulomas may look similar.
Treatment is directed at eradicating the underlying mycobacterial infection.
Currently, for patients with active tuberculosis, four-drug therapy with isoniazid, rifampin, pyrazinamide and ethambutol is recommended to avoid development of resistance. PNT responds promptly to appropriate anti-tuberculosis therapy. New lesions cease forming within days to weeks after therapy is initiated and existing lesions heal rapidly, usually within several months. A minimum of 6 months of anti-tuberculosis therapy is recommended. Recurrences appear rarely if at all after appropriate therapy.