Lichen scrofulosorum mimicking lichen planus.

Lichen scrofulosorum is the most uncommon clinicopathologic variant of the tuberculids. Usually, the eruption appears in children and adolescents with strong immune sensitivity to Mycobacterium tuberculosis and consists of tiny follicular papules, closely resembling lichen nitidus. We report a case of lichen scrofulosorum in an adult male with active cervical scrofuloderma who developed lesions of lichen scrofulosorum mimicking clinically lichen planus. Histopathologic study demonstrated granulomas around the hair follicles, although acid-fast bacilli stains, immunohistochemical stain for mycobacteria, polymerase chain reaction investigations and cultures failed to demonstrate Mycobacterium tuberculosis in the cutaneous lesions. The most striking features of the reported case were the onset of the eruption in an adult patient and the clinical appearance of the lesions, resembling lichen planus.