Answer To The Photo Quiz

Abstract

Diagnosis: borderline leprosy. The diagnosis of was suspected on the basis of the presence of erythematous annular skin lesions associated with hypoesthesia in a woman originating from the Philippines, where Mycobacterium leprae infection is endemic. It was confirmed by punch biopsy of an active skin lesion on the forehead (figure 1), which revealed granulomatous dermatitis, neural inflammation, and easily identifiable acidfast bacilli (AFB) (figure 2). Bacterial and fungal cultures were sterile. Leprosy, also known as Hansen disease, is a chronic granulomatous infection of the skin and peripheral nerves by the noncultivable obligate intracellular pathogen M. leprae. Globally, the majority of cases occur in India, South America, and Southeast Asia [1], In North America, it is usually seen among immigrants from regions where the disease is endemic and typically occurs within the first year after arrival [2]. Unfamiliarity with this disease may lead to delayed diagnosis, as in this case. Humans are the major reservoirs of M. lepraey although infection can occur in other animals (e.g., the 9-banded armadillo and monkeys) [3]. The proposed major route of human transmission is by aerosolized nasal droplets. Direct skin contact plays little, if any, role [1]. After exposure, 95% of individuals do not develop overt disease; the remainder progress to an leprosy stage, characterized by a single, ill-defined, hypopigmented skin lesion [2]. Most of these persons then experience spontaneous resolution of their lesions. However, approximately 25% of individuals who experience indeterminate progress to one of the classical forms of leprosy, which form a clinical spectrum that reflects the interplay between host immune response and pathogen. Tuberculoid leprosy, which is characterized by a robust Thl-like cell immunity with scant or no AFB in the lesions, and lepromatous leprosy, which is characterized by a predominant Th2-like humoral immunity with abundant AFB in lesions, are at the extremes of the clinical spectrum; the intermediate variants (borderline tuberculoid, midborderline, and borderline lepromatous) complete the gradient [2]. It is speculated that our patient's initial response to the topical corticosteroid therapy was related to an attenuation of the inflammatory response in the skin. The identification of AFB on skin biopsy sections stained by the modified Ziehl Neelsen stain (Wade-Fite) can confirm the