A 46-year-old obese man comes to the emergency room because of paresthesias in his feet and a hypopigmented skin lesion on his knee that he first noticed 6 weeks ago. He has also had fever, fatigue, and malaise for the last week. He has a history of chronic autoimmune thyroiditis for which he takes levothyroxine. He immigrated from Indonesia 3 years ago to join his family in the United States. His temperature is 38.7°C (101.7°F) and blood pressure is 122/84 mm Hg. Physical exam shows a well-defined hypopigmented skin lesion approximately 3 cm in diameter over the anterior aspect of the right knee. The area has no hair growth and remains dry although he is diaphoretic. There is diminished sensation to light touch and pinprick in the skin lesion when compared to surrounding skin. There is reduced light touch sensation in the big toes bilaterally. A full-thickness skin biopsy confirms the diagnosis. Which of the following organisms is the most likely cause of this patient's condition?

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Eductional Objective: The severity of leprosy, a systemic illness caused by Mycobacterium leprae, depends on the strength of the cell-mediated immune (CMI) response, with tuberculoid leprosy representing the milder form (intact Th1 CMI response) and lepromatous leprosy, the more severe form (weak CMI response).

A 46-Year-Old Obese Man Comes to the Emergency Room Because