Diagnosis: Papulonecrotic tuberculids
Description: Necrotizing papules on the knee and legs
Morphology: Papules
Site: Leg
Sex: M
Age: 45
Type: Clinical
Submitted By: Shahbaz Janjua
Differential DiagnosisHistory: Papulonecrotic tuberculids (PNT) were first described by Darier in 1896. Tuberculids represent a cutaneous hypersensitivity reaction or an exaggerated host immunologic response to TB antigens released from a distant focus of infection. Most patients react markedly to the Mantoux skin test. PNT is a chronic, recurrent, and symmetric eruption of necrotizing skin papules arising in crops, involving primarily extensor surfaces, particularly the knees, the elbows, and the dorsa of the hands and the feet. The lesions heal with varioliform scarring.