Clinicodermoscopic features of lichen scrofulosorum – A rare form of cutaneous tuberculosis

A 35-year-old male presented with multiple asymptomatic, skin-colored to erythematous, grouped, and discrete follicular papules of size ranging from 3 to 5 mm, mostly over the trunk for 15 days [Figure 1a]. There was no history of cough, fever, night sweats, weight loss or any other systemic complaints. He denied any past or family history of tuberculosis. Bacillus Calmette-Guerin scar was present on his left arm. Systemic examination was unremarkable.

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Figure 1:

(a) Multiple, skin-colored to erythematous, grouped, and discrete follicular papules. (b) Dermoscopy (DermLite, DL4, ×10 magnification) under polarized mode showing pale round monomorphic grouped perifollicular large dots with a central black follicular plug with perilesional erythema. (c) Histopathology showing perifollicular and perieccrine non-caseating tuberculoid granuloma (Hematoxylin and Eosin, ×400). (d) Complete resolution of the lesion after six months of antitubercular treatment.

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Dermoscopy under polarized light (DermLite, DL4, ×10 magnification) revealed pale round monomorphic grouped perifollicular large dots with a central black follicular plug with perilesional erythema [Figure 1b]. Differential diagnoses of lichen scrofulosorum, papular mucinosis, papular sarcoidosis, and histoid leprosy were kept. Mantoux test showed 3 mm induration after 48 h. The biochemical, hematological, and radiological investigations were within normal limits. Histopathology revealed superficial non-caseating tuberculoid granuloma around hair follicles and sweat ducts [Figure 1c]. Based on clinical and histopathological findings, a final diagnosis of lichen scrofulosorum was kept, and the patient was started on antitubercular treatment (ATT) with complete resolution after six months [Figure 1d]. Our case presented with typical morphology, dermoscopic, and histopathologic picture. Although the Mantoux test was negative, there was a complete response to ATT.