A 23-year-old man presented with a five-month history of a slightly pruritic eruption on his right elbow (see the accompanying figure). He had taken a 15-day course of itraconazole (Sporanox), in a dosage of 200 mg per day, and had applied econazole (Spectazole) cream twice a day for 15 days and ketoconazole (Nizoral) cream twice a day for one month without improvement. He noted that his skin felt numb in the area of the eruption.
On physical examination, the patient was found to have a 25 cm × 20 cm annular plaque with an indurated border and some central clearing on the right antecubital fossa.
The answer is B: Hansen's disease. A skin biopsy showed tuberculoid leprosy. The patient was treated with dapsone, 100 mg per day, and rifampin, 600 mg per month for six months.
Hansen's disease is a chronic granulomatous disease caused by Mycobacterium leprae that affects the skin and nerves.1 It is estimated that 1.15 million cases exist worldwide; in the United States, southern Louisiana and Texas are considered endemic for leprosy.2,3 The mode of transmission is postulated to be through the nasal mucosa of untreated persons with leprosy and may also involve direct skin-to-skin contact, as well as exposure to the nine-banded armadillo.3,4
Clinically, two helpful features are a cutaneous eruption and areas of cutaneous anesthesia.1 Other features are nerve enlargement, nasal stuffiness, inflammatory eye changes and loss of lateral eyebrows.5 Depending on the immune response of the host, leprosy can manifest in several different ways, ranging from tuberculoid to lepromatous leprosy, including indeterminate and borderline types.3 Tuberculoid leprosy, as in this patient, usually presents as a single sharply demarcated, hypopigmented, hypoesthetic macule with a circinate, elevated border. Often the nerves at the edge of the lesion are thickened, and peripheral nerves can be enlarged.1 Lepromatous leprosy is more generalized, involving the skin, upper respiratory mucosal membranes, reticuloendothelial system, adrenal glands and testes. Lesions are small, ill-defined, bilaterally symmetric, flesh-colored, erythematous or slightly hypopigmented macules, which progress to papules, plaques, nodules and diffuse thickening of the skin.3
Diagnosis is made by demonstrating leprosy bacilli in the skin. It is preferable to get a skin biopsy from the affected area and a special stain (such as the Fite stain, a modified acid-fast stain) for leprosy must be requested.3 Because of high resistance worldwide, the World Health Organization recommends multidrug therapy: three drugs for treatment of lepromatous leprosy limited to five years (dapsone, 100 mg per day; rifampin, 600 mg per month; and clofazimine (Lamprene), 50 mg per day.4 Tuberculoid leprosy is treated with dapsone, 100 mg per day, and rifampin, 600 mg per month, for six months.3,5
The other choices (granuloma annulare, mycosis fungoides, sarcoidosis and tinea corporis) may also present as one or more annular plaques, similar to those seen in leprosy. A potassium hydroxide mount of the skin scrapings of tinea corporis would reveal numerous hyphae, thus differentiating it from the other disorders. In this patient, the history of no improvement after treatment with topical and oral antifungal agents would make tinea corporis an unlikely diagnosis. His complaint of numbness in the area of the lesions is a clue for the diagnosis of leprosy. Because all of these disorders can look similar clinically, a skin biopsy is necessary to make a definitive diagnosis.