Sub-polar lepromatous leprosy localized to the face

Leprosy is an infectious disease characterized by a wide spectrum of clinical manifestations, ranging from tuberculoid to lepromatous disease with immunologically unstable borderline forms in between. In clinical practice cases often do not conform to a classical textbook description, which may lead to misdiagnosis if not properly investigated. A 22-year-old patient presented to us with erythematous plaques localized to the face. Slit skin smear for Mycobacterium leprae was positive from lesional as well as non-lesional skin. A biopsy from a plaque showed diffuse atrophy of the epidermis with a subepidermal cell free zone (grenz zone). The cellular infiltrate was composed of foamy macrophages admixed with lymphocytes in the dermis. Fite-Faraco staining revealed clumps of acid-fast bacilli within the macrophages. Based on the skin smear and histopathology findings, a diagnosis of sub-polar lepromatous leprosy was made and the patient was started on multidrug therapy. The exact pathogenesis of localized multibacillary disease is not known. Our case highlights the importance of skin smear and biopsy in all suspected cases of Hansen disease. We conclude that routine skin smear in all new leprosy cases is mandatory to differentiate localized multibacillary cases from paucibacillary cases for the purpose of accurate categorization and treatment.