Background  Lichen scrofulosorum is considered a rare form of cutaneous tuberculosis. Current information is based on case reports and case series with a small number of patients.

Methods  Thirty-nine patients with Lichen scrofulosorum were followed during the period January 1996 to December 2002. Clinical details (age, sex, duration of disease, associated tubercular lesions, extent and distribution of skin lesions), laboratory parameters (hemoglobin, total leucocytic counts, erythrocyte sedimentation rate, Mantoux test, presence of BCG scar), and response to antitubercular treatment were recorded and analyzed.

Results  7.6% patients of all (511) patients with cutaneous tuberculosis had LS. 22 (56.4%) were males and 32 (84%) were below 15 years of age. Twenty-eight (72%) had an associated focus of tuberculosis elsewhere in the body; 13 (33%) had tubercular lymphadenopathy, while 11 (28%), three (8%) and six (15%) had pulmonary tuberculosis, intracranial tuberculosis and other forms of cutaneous tuberculosis, respectively. Six (15%) had tubercular focus at multiple sites. Eleven (28%) had no other identifiable focus of tuberculosis. Twenty-eight (72%) had evidence of receiving BCG vaccination. Trunk was the commonest (100%) affected site. The two groups with and without associated tubercular focus were not different with respect to age, sex, duration of disease, hemoglobin, total leukocyte count, erythrocyte sedimentation rate, Mantoux test positivity, and presence of BCG scar. Mycobacteria tuberculosis could not be detected either on acid fast bacilli (AFB) staining or on culture from biopsies of LS lesions. All patients (including those without evidence of tubercular focus) responded to antitubercular treatment, signifying an underlying occult tubercular focus as etiology.

Conclusions  Lichen scrofulosorum is an uncommon but not rare cutaneous manifestation of tuberculosis. A high index of suspicion and awareness is required for diagnosis. Systemic tuberculosis is often associated with LS and a prior BCG inoculation does not protect against development of LS. Response to antitubercular treatment is good irrespective of the presence or absence of associated tubercular focus.