Papulonecrotic tuberculid: a rare form of cutaneous tuberculosis

We describe a case of papulonecrotic tuberculid, a rare form of cutaneous tuberculosis, in a 25-year-old Philippino woman who had immigrated to Canada 8 years previously. The patient presented with a 3-week history of tender left cervical adenopathy; 1 week later, she developed multiple ulcerated erythematous nodules and emboluslike lesions scattered over her fingers. Results of a biopsy performed on the lymph node revealed granulomatous lymphadenitis, and Mycobacterium tuberculosis grew from the lymph node. Histopathologic analysis of an ulcerative finger lesion demonstrated nonnecrotizing granulomas with dense lymphocytic inflammation of the superficial dermis; however, results of acid-fast staining, mycobacterial culture, and polymerase chain reaction for M tuberculosis complex were all negative. Different conditions can mimic papulonecrotic tuberculid. Therefore, the diagnosis can be difficult unless M tuberculosis is isolated from a site other than the skin, because stain and culture results from skin biopsy specimens are typically negative and the polymerase chain reaction is positive in only 50% of cases. We review the epidemiology, clinicopathologic features, and differential diagnosis of papulonecrotic tuberculid. Awareness of this entity is important to distinguish it from other conditions and to institute appropriate therapy in a timely fashion.