Lichen scrofulosorum.

A 12-month-old boy with pulmonary tuberculosis developed a papular lichenoid eruption which showed epithelioid granulomas on histology, consistent with lichen scrofulosorum. Stains and cultures for mycobacteria in the skin were negative, and a polymerase chain reaction (PCR) analysis failed to detect the DNA of Mycobacterium tuberculosis in a skin biopsy specimen, thus making lichen scrofulosorum one of the remaining manifestations of M. tuberculosis infection in which evidence of the bacillus has not been found to date. Lichen scrofulosorum is now considered a rare form of tuberculid but should not be neglected.