Molluscoid skin lesions in histoid leprosy with pseudo‐isomorphic Koebner phenomenon
Authors: Ghorpade Ashok 
Published: November 2008

A 30‐year‐old Indian man presented with multiple asymptomatic skin lesions on the arms, buttocks, trunk, and knees of 4 months’ duration. These lesions had started over the right arm and gradually increased in number and spread to involve the other sites. There was no history of any skin lesions in the past. Family members were normal.

 Cutaneous examination showed multiple, skin‐colored, shiny papules abruptly arising over the surrounding normal skin of the arms, buttocks, legs, trunk, and pinnae, varying from 2 to 3 mm in size. Some of the papules over the trunk and arms showed central umbilication resembling molluscum contagiosum, and a few showed superficial erosions and/or crusting (Fig. 1a,b). A few similar, erythematous papules over the left buttock showed a linear distribution, suggestive of pseudo‐isomorphic Koebner phenomenon (Fig. 2a,b). There was hypoesthesia in the distal part of the arms and legs for thermal, touch, and pain sensation, and the bilateral lateral popliteal and ulnar nerves were thick and mildly tender. The clinical features were suggestive of histoid leprosy. Systemic and eye examination were normal. Routine hematology and liver and kidney function tests were normal, and blood venereal disease research laboratory (VDRL) test and enzyme‐linked immunosorbent assay (ELISA) for human immunodeficiency virus (HIV) 1 and 2 were negative. Histopathology from a papular lesion showed a thinned out epidermis, flattened rete ridges, a subepidermal Grenz zone, and granulomas of closely packed, spindle‐shaped histiocytes arranged in whorls, with foamy macrophages. In addition to the above histologic findings, the molluscoid lesion also showed an epidermal erosion with acid‐fast bacilli demonstrated by Ziehl–Neelsen stain (Fig. 3a,b). Slit skin smear examination from both the ear lobes and umbilicated lesions was highly positive, with a bacillary index (BI) of 6+ (> 1000 bacilli per oil immersion field) and a morphologic index (MI) of 80% (Fig. 3c). A diagnosis of histoid leprosy was made. The patient was treated with daily rifampicin and ofloxacin for 2 months, followed by standard multibacillary (MB) multidrug therapy (MDT) with daily dapsone and clofazimine with monthly rifampicin for 2 years. An excellent response to treatment was obtained with regression of all the skin lesions.

(a) Umbilicated and shiny papular skin lesions arising abruptly over normal skin. (b) Umbilicated, crusted, and eroded pigmented lesions over the arm

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(a) Multiple shiny papular lesions over both buttocks, showing linearly arranged skin lesions on the outer aspect of the upper lateral quadrant of the left buttock. (b) Close‐up view of the linearly arranged papular skin lesions on the buttock

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(a) Histopathology from a ruptured umbilicated papule showing a thinned out epidermis with flattened rete ridges, an epidermal erosion in the center, a subepidermal Grenz zone, and granuloma of closely packed spindle‐shaped histiocytes arranged in whorls, with foamy macrophages (Ziehl–Neelsen stain; original magnification, ×40). (b) Close‐up view of the marked portion of (a) showing acid‐fast bacilli at the mouth of the ruptured area arranged in a globus and discretely, shown by red arrows (Ziehl–Neelsen stain; original magnification, oil immersion, ×1000). (c) Slit smear examination from a skin lesion showing long, thick, acid‐fast bacilli, arranged in clumps and discretely (Ziehl–Neelsen stain; original magnification, oil immersion, ×1000)

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