A 25 year old man presents with a single, large, hypopigmented patch which extends from his left thigh up to his knee, for 2 years. There is no associated pain or itching, nor is there a history of trauma or chemical exposure to the affected area. He migrated from Brazil to the United States 4 years ago. There is no recent history of foreign travel. His medical history is unremarkable. He has a single stable sexual partner.
Nerve conduction velocities are within normal parameters.
Lateral Flow test is positive for IgM antibodies for M. leprae
The smear of the lesion reveals a bacterial Index (BI) of 4+. Smears from the ear lobes, thigh and arm are negative. The skin biopsy reveals epidermal atrophy and mild orthokeratosis. Small aggregates of histiocytes and lymphocytes are seen around the vessels, skin adnexa, and in and around the nerves. The granuloma fraction is 5%; solid acid fast bacilli are seen in some, both singly and in small clusters of 3 to 5 bacilli; the BI of the granuloma is 2+.