Lepromatous leprosy in erythema nodosum leprosum reaction mimicking Sweet’s syndrome

Abstract

A 52-year-old Malay man presented with an acute one week history of multiple erythematous papules and nodules on the limbs, trunk, and face. On physical examination, he had multiple erythematous nontender, nonpruritic nodules and plaques on the trunk, limbs, and forehead (Fig. 1). A few nodules showed pustulation and ulceration (Fig. 2). He was febrile at 38 °C. Systemic review and general examination were normal. There were no thickened nerves, neurological deficits, or deformities of the hands or feet. Eyes and oral mucosa were normal. Erythematous plaques and nodules on the trunk Erythematous plaque with pustule and healing ulcer The initial clinical impression was that of Sweet’s syndrome in view of the acute onset of typical lesions and fever. Complete blood count revealed marked leukocytosis (24.1 × 103/μl) with predominant neutrophilia (87.5%). Erythrocyte sedimentation rate (ESR) was markedly raised. Differential diagnoses included cutaneous lymphoma and infective causes, such as cutaneous tuberculosis, multibacillary leprosy, and nontuberculous mycobacterial or subcutaneous fungal infection. Skin biopsy confirmed the diagnosis of lepromatous leprosy with erythema nodosum leprosum reaction. The histology showed a Grenz zone with granulomas throughout the dermis, consisting of foamy macrophages with globi of bacilli within. Focal areas showed thrombosed vessels with necrosis of vessel walls and numerous neutrophils. Fite stain was positive for leprae bacilli (Fig. 3). Direct immunofluorescence showed granular deposits of IgA and C3 in the upper and lower dermal blood vessel walls, consistent with vasculitis. Histology showed granulomas with Mycobacterium leprae bacilli-laden macrophages (Fite stain, original magnification ×400) Slit skin smear confirmed the presence of Mycobacterium leprae with a Bacteriological Index of 5+ and a Morphological Index of <1%. Leprosy has been controlled in Singapore for many years. This has been achieved by a good program for control of leprosy. The latest reported incidence of leprosy is low at 0.1 per 100,000 resident population.1 Only 10 cases were reported in 2008, mostly among foreign workers. Most patients with multiple nodules would have been biopsied and diagnosed early. This patient recalled having multiple asymptomatic skin lesions for two years but did not seek specialist opinion. Erythema nodosum leprosum reactions may occur spontaneously in longstanding lepromatous leprosy,2 but for it to simulate Sweet’s syndrome is much less common, though it was reported as early as 1987 by Kuo and Chan.3 In the patient described, the clinical and histopathological features were consistent with both lepromatous leprosy and Sweet’s syndrome. It was suggested that leprosy in a reactional state should be considered as a differential diagnosis for Sweet’s syndrome. In our patient, the histology showed numerous neutrophils but was otherwise not consistent with Sweet’s syndrome. Clinically, the lesions mimicked Sweet’s syndrome sufficiently for it to be considered as one of the likely differential diagnoses. Fever, neutrophilia, and rapid response to oral corticosteroids were observed, as are expected in Sweet’s syndrome.4 In this patient, the diagnosis was clinched on histopathological examination. Reactional states of leprosy are known to present in many ways. The skin manifestations of a type 2 lepra reaction typically appear in normal skin between previously recognized plaques of borderline or lepromatous leprosy.5 In this case, the reactional lesions were the presenting symptom. As he did not have a preceding diagnosis of leprosy, this was an unexpected finding. Most reported cases mimicking Sweet’s syndrome have prior diagnosis of borderline or lepromatous leprosy.6 This patient was treated with WHO-recommended drugs for lepromatous leprosy. The erythema nodosum leprosum reaction was controlled with oral corticosteroids and clofazimine. Corticosteroid dose was gradually reduced, with no recurrence in 12 months of follow-up. This locally uncommon infection presented in an unusual manner, making this a case with valuable learning points. Delayed diagnosis of leprosy leads to significant morbidity7 and has important public health consequences. With this case, we highlight the unusual Sweet’s syndrome-like presentation of lepromatous leprosy in erythema nodosum leprosum reaction and the need to exclude infectious diseases, even in a nonendemic area.