LAUSR

ment for 6 months, and after 4 weeks the lesions healed, some leaving atrophic scars. A diagnosis of two coexisting tuberculids (PNT and LS) associated with mediastinal tuberculous lymphadenopathy was made, suggested by: failure to detect M. tuberculosis in skin biopsies; the presence of detectable extracutaneous M. tuberculosis infection; a strongly positive tuberculin skin test and a positive interferon-gamma release assay; histopathologic evidence of granulomatous inflammation; resolution of lesions with antituberculosis therapy. Papulonecrotic tuberculid is the most common tuberculid and typically presents as a symmetric and recurring eruption of firm violaceous papules that subsequently become necrotic. On the other hand, LS presents with crops of firm 1–5 mm, asymptomatic, grouped, follicular papules. Both PNT and LS are most frequently seen in children and young adults. Histopathologic examination demonstrates epithelioid granulomatous inflammation, which in LS patients is in the upper dermis and around dermal appendages without necrosis and in PNT associated with wedge-shaped necrosis of the upper dermis/epidermis and lymphocytic vasculitis. An extracutaneous focus of tuberculosis (most frequently nodal, pulmonary, or skeletal) is detectable in 38–75% and 72% of PNT and LS cases, respectively. Patients improve within days to weeks following anti-TB therapy, although lesions may spontaneously resolve even without treatment. The reaction pattern of tuberculids is not fully understood and, probably, is highly individualized. Most cases report a single tuberculid reaction throughout the disease, including a case of a child with PNT transforming into LS, but few cases had coexistence of two tuberculids. The majority of them correspond to concomitant LS and EIB or PNT and EIB. The coexistence of LS and PNT is rarely reported in literature, with only three cases described. Chuang et al. suggested that they may represent a morphologic continuum and different levels of immune complex-mediated vasculitis, followed by a delayed hypersensitivity reaction. Correct diagnosis of LS and PNT is frequently delayed because of its rarity, benign appearance, and clinical similarity to more common skin conditions. Widespread awareness and high index of suspicion of tuberculids can be crucial in the early detection and treatment of an occult tuberculous focus.