By Gary M. White, MD
Papulonecrotic tuberculid (PT) is a tuberculin that presents as multiple papules in a child or young adult. Tuberculids are cutaneous eruptions associated with infection by tuberculosis in which there are no viable organisms in the skin. More specifically, a tuberculid may be defined as a skin change with the following characteristics: 1) associated with internal Tuberculous infection, 2) positive PPD, 3) absence of bacilli in the skin biopsy specimen or culture, and 4) healing of the skin with remission of the tuberculous infection.
Recurring crops of hard, red, crusted papules 2-8 mm. in a patient infected with tuberculosis is characteristic. Central ulceration or necrosis is typical. Lesions involute over weeks, leaving varioliform scars. Symmetric involvement of the limbs is typical with special preference for the elbows and knees. The Mantoux test is usually strongly positive. PCR has shown M. tuberculosis DNA in biopsy specimens.
Eruptions which may also present similarly with widespread papules include PLEVA, lymphomatoid papulosis and papular urticaria.
The lesions usually show a dramatic response to antituberculous therapy.
An 11-year-old Chinese boy with recurrent ‘boils’ on his face, forearms, and thighs without low fever or cough for 1 month. His uncle had pulmonary tuberculosis. Papules, pustules and ulcers were scattered on the body. A chest X-ray showed a cord-like shadow and ‘sclerosis.’ The PPD was strongly positive. The Mycobacterium tuberculosis antibody (TB-IgG was positive. Mycobacterium tuberculosis DNA sequences were confirmed by real-time polymerase chain reaction (Real-Time PCR) using slices of wax block of the lesion. Treatment was begun with isoniazid, 300 mg/day, pyrazinamide, 750 mg/day, and rifampin, 450 mg/day, for 2 months and was followed by isoniazid, 300 mg/day, and rifampin, 450 mg/day, for 4 months. One month later, all the lesions had regressed. Indian J Dermatol. 2013 Jan-Feb; 58(1): 85
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