Sporotrichoid lupus vulgaris

A 10-year-old boy presented with multiple, asymptomatic, and raised skin lesions over his right lower limb. These lesions first appeared on the plantar surface of his right foot 2 years ago. He could not recollect any history of thorn prick. Further, these lesions extended upward to his inner leg, increasing both in number and size. There was a history of scarring at one end of the lesions and extension from the other. Examination of the right lower limb revealed scaly erythematous plaques of varying sizes with central scarring and peripheral nodularity extending in a linear array from the plantar surface of the right foot to the medial aspect of the upper leg in a sporotrichoid pattern [Figure 1]. There was matted unilateral inguinal lymphadenopathy. Hematological investigations were within normal limits. Serology for human immunodeficiency virus 1 and 2 was non-reactive.

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Figure 1:

Plaque from the right foot to inner leg in a sporotrichoid pattern.

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Chest radiograph posteroanterior view and radiograph of the right foot were normal. Mantoux test showed 20 mm induration. The culture for Mycobacterium tuberculosis was not done. Histopathology revealed hyperkeratosis, acanthosis, and elongation of the rete ridges with dense dermal granulomas comprising epithelioid cells, Langhan’s type giant cells, and chronic inflammatory cells close to the epidermis [Figure 2]. Periodic acid Schiff stain for fungus was done and turned negative. Based on the clinical and histopathological correlation, a final diagnosis of “Sporotrichoid lupus vulgaris” was made. Sporotrichoid form of lupus vulgaris is a rare and unusual variant^[1] and mimics sporotrichosis. Tuberculosis bacilli follow the lymphatic channels and during transit, provoke cutaneous granulomatous inflammation resulting in a linear array of papular, nodular, and ulcerative lesions over time. He was started on antituberculosis treatment according to NTEP guidelines for 2022. The lesions started to regress by 6 weeks [Figure 3].

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Figure 2:

Histopathology showing granulomas comprising epitheloid cells and Langhan’s type giant cells close to the epidermis (H and E Stain, 10 × 10).

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Figure 3:

Clinical regression of the plaques after 6 weeks of antituberculosis therapy.

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