A 42-year-old man comes to the office due to a nonpruritic, nonpainful skin lesion on the left upper arm that began 2 months ago. He has also had tingling and numbness of the left fingers. The patient has no medical history and does not take any medications. He emigrated from Southeast Asia to Connecticut a year ago. Temperature is 36.6 C (97.8 F), blood pressure is 126/82 mm Hg, and pulse is 74/min. Skin examination shows a 4-cm, well-circumscribed, hypopigmented patch on the left upper arm with no sensation to pinprick. The ulnar nerve is thickened and tender at the left elbow. Touch and pain sensation is absent in the left ulnar nerve distribution. Which of the following is most likely to confirm the diagnosis in this patient?

Question

A 42-year-old man comes to the office due to a nonpruritic, nonpainful skin lesion on the left upper arm that began 2 months ago.  He has also had tingling and numbness of the left fingers.  The patient has no medical history and does not take any medications.  He emigrated from Southeast Asia to Connecticut a year ago.  Temperature is 36.6 C (97.8 F), blood pressure is 126/82 mm Hg, and pulse is 74/min.  Skin examination shows a 4-cm, well-circumscribed, hypopigmented patch on the left upper arm with no sensation to pinprick.  The ulnar nerve is thickened and tender at the left elbow.  Touch and pain sensation is absent in the left ulnar nerve distribution.  Which of the following is most likely to confirm the diagnosis in this patient?

Quizplus · Accepted Answer

11ec25c8_d45e_4f95_bc81_17492557727f_MD0003_00 Leprosy is a chronic granulomatous disease of the skin and peripheral nerves caused by the acid-fast bacillus Mycobacterium leprae. Transmission is thought to occur via respiratory droplets, although cases are occasionally linked to close contact with a nine-banded armadillo. Infections are rare in the United States and occur primarily in immigrants or travelers to endemic regions (eg, Asia, Africa, South America). Manifestations include >1 chronic, anesthetic, macular (often hypopigmented) skin lesions with raised, well-demarcated borders. Nearby nerves often become nodular and tender, and segmental demyelination may result in loss of sensation and motor function. Diagnosis is clinical in endemic regions, but in the United States patients usually require a full-thickness biopsy of the skin lesion edge (as M leprae is not culturable). Patients with minimal lesions ("paucibacillary") are treated with dapsone and rifampin; those with extensive lesions ("multibacillary") require the addition of clofazimine. Lesions often take months or years to heal completely. > (Choice A) Lyme disease typically manifests with erythema migrans, a slowly spreading erythematous lesion with central clearing ("bulls-eye" lesion). Sensory or motor neuropathy may sometimes occur in early disseminated disease. Nerve thickening and tenderness with an anesthetic lesion are more likely to indicate leprosy. (Choice B) KOH scrapings can diagnose dermatophytes (eg, Tinea corporis) and Candida albicans. T corporis causes "ringworm," which manifests as a pruritic, scaly plaque that spreads centrifugally, leaving a cleared center. Anesthesia, nerve nodularity/pain, and paresthesias are not typically a feature of these fungal infections. (Choice C) Nerve conduction studies are likely to be abnormal (decline in conduction velocity) but would not provide a diagnosis; a skin biopsy is required for diagnosis. (Choice E) Primary syphilis is characterized by a painless chancre (shallow, nonpurulent ulcer with raised, well-demarcated borders). Tertiary syphilis may cause skin gummas (soft, ulcerative masses with necrotic centers). Neither primary nor tertiary syphilis is commonly associated with localized anesthesia or nodular peripheral nerves. (Choice F) Mycobacterium tuberculosis can rarely cause skin manifestations, including ulcers, nodules, and warty plaques. A hypopigmented, anesthetic patch with nerve nodularity/pain is more likely to be leprosy. Educational objective: Leprosy is a chronic granulomatous disease of the skin and peripheral nerves that is found primarily in developing regions. Symptoms include chronic, anesthetic, hypopigmented lesions with peripheral nerve involvement (nodular/painful nerve deformations with diminished sensory/motor activity). Diagnosis usually requires a biopsy from the active edge of the lesion.

A 42-Year-Old Man Comes to the Office Due to a Nonpruritic