A 34-year-old woman comes to the office due to skin changes. Blotches of skin on her arms appear to be of a different color, and she also has a tingling sensation in her hands. These symptoms have developed over the past several months. The patient has no other past medical history. She is a political refugee from East Africa. On examination, there are patchy areas of skin anesthesia and hypopigmentation on her upper extremities. Nerve biopsy evaluated under light microscopy shows many organisms invading Schwann cells. HIV testing is negative. Which of the following organisms is the most likely cause of this patient's condition?

Question

A 34-year-old woman comes to the office due to skin changes.  Blotches of skin on her arms appear to be of a different color, and she also has a tingling sensation in her hands.  These symptoms have developed over the past several months.  The patient has no other past medical history.  She is a political refugee from East Africa.  On examination, there are patchy areas of skin anesthesia and hypopigmentation on her upper extremities.  Nerve biopsy evaluated under light microscopy shows many organisms invading Schwann cells.  HIV testing is negative.  Which of the following organisms is the most likely cause of this patient's condition?

Quizplus · Accepted Answer

11ec160b_37eb_4783_9249_bddbcc491e85_MD0001_00 Leprosy (Hansen disease), a deforming infection primarily of the skin and nerves, is caused by Mycobacterium leprae. Transmission is promoted in unhygienic conditions and likely occurs through the respiratory route, with some organisms being transmitted through prolonged direct skin-to-skin contact. Infection has also been associated with armadillo contact in the southwestern United States. The range of clinical manifestations depends on the strength of the cell-mediated immune (CMI) response. M leprae grows best at temperatures below core body temperature, partially explaining why leprosy manifests in the skin, superficial nerves (eg, Schwann cells in this patient), eyes, and testes. Intermediate features between TT and LL are often seen. (Choice A) Borrelia burgdorferi causes Lyme disease. Symptoms include a characteristic skin rash (erythema chronicum migrans) with fever and malaise. Systemic disease can progress to cause arthritis, facial paresis, or cardiac involvement (eg, conduction abnormalities). Prolonged untreated disease can lead to central nervous system involvement. (Choice B) Campylobacter fetus, a gram-negative rod, causes mild enteritis in immunocompetent patients and mild systemic bacteremic illness in immunocompromised patients. (Choice C) Corynebacterium diphtheriae is a gram-positive rod that causes diphtheria, a primarily toxin-mediated lower respiratory tract infection that is sometimes complicated by polyneuritis and myocarditis. (Choice E) Treponema pallidum causes syphilis. Primary syphilis manifests as a painless chancre at the inoculation site. Secondary syphilis results in erythematous macules over the entire body (including the palms and soles) and condyloma lata formation. Tertiary syphilis results in skin and bone gummas and ascending aortitis. Educational 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 34-Year-Old Woman Comes to the Office Due to Skin