Answer to Image of the Month November 2012
Lichen scrofulosorum
An epithelioid cell granuloma has entirely replaced the hair follicle whose only remnants are small strips of arrectore pilorum in the adjacent dermis.
In other cases, the granuloma may not be seen in its entirety in a single section with parts of the follicle being replaced/surrounded by the granulomatous infiltrate. Granulomas may also be seen elsewhere in the dermis, in the papillary dermis and around sweat glands.
Clinically, lichen scrofulosorum presents as grouped, small papules and papulo-pustules on the trunk. The papules usually show tiny central crusts. When crusts are absent, lichen nitidus may be a close clinical differential diagnosis. The Mantoux test is often strongly positive. An extra-cutaneous focus of tuberculosis can be detected in most patients and anti-tubercular therapy leads to resolution of both the tubercular focus and lichen scrofulosorum
Grouped, small papules with crusts
Lichen nitidus-like papules