Leprosy, known as the “great imitator”, can present with systemic inflammatory manifestations that closely resemble autoimmune diseases, particularly during type 2 leprosy reactions (erythema nodosum leprosum, ENL). We report a 23-year-old Chinese male with a 5-year history of recurrent fever, arthralgia, papular and nodular skin lesions, and generalised lymphadenopathy. He met Yamaguchi criteria for adult-onset Still’s disease (AOSD) and received prolonged immunosuppressive therapy with glucocorticoids, methotrexate, hydroxychloroquine, and adalimumab but experienced recurrent flares upon steroid tapering. Skin biopsy from a right costal margin lesion revealed a dense dermal infiltrate predominantly composed of foamy histiocytes, with collagen degeneration and periadnexal lymphohistiocytic inflammation. Well-formed granulomas were absent. Acid-fast staining (Ziehl-Neelsen) demonstrated abundant acid-fast bacilli within the foamy histiocytes forming characteristic globi, and Wade-Fite stain confirmed Mycobacterium leprae with a high bacterial index. The diagnosis was revised to lepromatous leprosy with type 2 reaction (ENL). After referral for multidrug therapy (MDT) and gradual prednisolone tapering, the patient achieved complete clinical remission with normalisation of inflammatory markers. This case underscores a critical diagnostic pitfall for dermatopathologists and clinicians: in non-endemic regions where clinical suspicion for leprosy is low, the histopathologic finding of a foamy histiocytic infiltrate without granuloma formation should prompt acid-fast staining to exclude lepromatous leprosy, particularly in patients with unexplained systemic inflammation and epidemiologic risk factors.
BT - Leprosy Review DA - 09/2026 DO - 10.47276/lr.97.3.2026049 IS - 3 LA - ENG M3 - Article N2 -Leprosy, known as the “great imitator”, can present with systemic inflammatory manifestations that closely resemble autoimmune diseases, particularly during type 2 leprosy reactions (erythema nodosum leprosum, ENL). We report a 23-year-old Chinese male with a 5-year history of recurrent fever, arthralgia, papular and nodular skin lesions, and generalised lymphadenopathy. He met Yamaguchi criteria for adult-onset Still’s disease (AOSD) and received prolonged immunosuppressive therapy with glucocorticoids, methotrexate, hydroxychloroquine, and adalimumab but experienced recurrent flares upon steroid tapering. Skin biopsy from a right costal margin lesion revealed a dense dermal infiltrate predominantly composed of foamy histiocytes, with collagen degeneration and periadnexal lymphohistiocytic inflammation. Well-formed granulomas were absent. Acid-fast staining (Ziehl-Neelsen) demonstrated abundant acid-fast bacilli within the foamy histiocytes forming characteristic globi, and Wade-Fite stain confirmed Mycobacterium leprae with a high bacterial index. The diagnosis was revised to lepromatous leprosy with type 2 reaction (ENL). After referral for multidrug therapy (MDT) and gradual prednisolone tapering, the patient achieved complete clinical remission with normalisation of inflammatory markers. This case underscores a critical diagnostic pitfall for dermatopathologists and clinicians: in non-endemic regions where clinical suspicion for leprosy is low, the histopathologic finding of a foamy histiocytic infiltrate without granuloma formation should prompt acid-fast staining to exclude lepromatous leprosy, particularly in patients with unexplained systemic inflammation and epidemiologic risk factors.
PB - Lepra PY - 2026 SP - 1 EP - 8 T2 - Leprosy Review TI - Lepromatous leprosy presenting as adult-onset Still's disease: a 5-year diagnostic challenge UR - https://www.researchgate.net/publication/413067992_Lepromatous_leprosy_presenting_as_adult-onset_Still's_disease_a_5-year_diagnostic_challenge/fulltext/6aae18b66b2ede2d2aab7d22/Lepromatous-leprosy-presenting-as-adult-onset-Stills-disease-a-5-year-diagnost VL - 97 SN - 2162-8807 ER -