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Papulonecrotic tuberculid. A clinical, histopathological, and immunohistochemical study of 15 patients.

We report 10 women and five men with papulonecrotic tuberculid, an uncommon form of cutaneous tuberculosis (TB). The mean age was 22.6 years (range, 2 1/2-35 years) at presentation. The Mantoux test was strongly positive in 13 patients. Five patients showed presumptive evidence of associated TB; in one case, the presence of TB was proven by culture. Response to anti-TB was dramatic in all cases. Clinical findings were similar to those previously published. We emphasize the simultaneous occurrence of erythema induratum, associated Takayasu's disease, possible associated phlebitic tuberculid, and clinical mimicry of acute bacterial endocarditis. The main histopathological findings obtained from 27 biopsy specimens included dermal necrosis (26 of 27 cases), a poorly formed granulomatous infiltrate (27 of 27 cases), vasculitis (11 of 27 cases), perivascular spongy edema (11 of 27 cases), and follicular necrosis or suppuration (five of 27 cases). A Ziehl-Neelsen stain was negative in all biopsy specimens. Immunohistochemical labeling revealed a preponderance of T-lymphocytes (UCHL-1+), monocytes-macrophages (S-100+), and Langerhans cells (ACT+), indicative of a type IV hypersensitivity reaction. B-lymphocytes (L26+) were sparse. Conditions that may be confused with PNT on clinical or histopathological ground include pityriasis lichenoides et varioliformis acuta, papular urticaria, papulopustular syphilide, miliary TB, septicemia, perforating granuloma annulare, chondrodermatitis nodularis, reactive perforating collagenosis, allergic granulomatosis, suppurative folliculitis, and infectious causes of palisading granulomas. Papulonecrotic tuberculid has distinct clinical, histopathological, and immunohistochemical features. Awareness of this entity is important since an appropriate diagnosis is necessary for the institution of timely curative treatment.