Lichen scrofulosorum: importance of early recognition.

Lichen scrofulosorum (LS), a tuberculid affecting children and young adults, usually presents with asymptomatic skin-coloured to erythematous follicular and perifollicular papules over the trunk and extremities. An underlying focus of tuberculosis can be detected, but occasionally other mycobacterial infections may be responsible. The eruption is associated with a positive tuberculin test or positive interferon-gamma release assay. Perifollicular granulomas and absence of bacilli are the histopathological characteristics. LS can go unsuspected because of its waxing and waning course and close resemblance to other dermatoses. This article reviews the different clinical presentations and various associations of LS. We reiterate that the focus of internal infection may be subtle and go undetected, emphasizing the need for correct diagnosis and early treatment.