Leprosy 2_0213 Derm Dx
A 35-year-old refugee from Bhutan, a country in South Asia, presents complaining of a hypopigmented skin patch on his right arm. He complains that the patch feels “dry” and that he has lost sensation within the patch.
On exam, he is a well-nourished, well-developed South Asian male. A complete physical exam is remarkable only for a hypopigmented patch on the right forearm without sensation. The patch feels slightly indurated. A biopsy is performed showing linear granulomas in the dermis following the course of a nerve.
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Leprosy – also known as Hansen’s disease – is a disease that has been recognized since ancient times. Leprosy is in fact mentioned in the Bible. There is a popular misconception that leprosy involves body parts and skin “falling off.” This notion is entirely false.
Leprosy is a worldwide disease, however it has been largely eradicated from most countries. Currently, Brazil, India and Indonesia represent 75% of all cases. In the United States, most cases reported occur in immigrants. However, leprosy is endemic to Louisiana, southeast Texas and neighboring regions where it is transmitted via exposure to armadillos.
Leprosy is caused by Mycobacterium leprae. M. leprae cannot be cultured in a laboratory. It can be cultivated in mouse footpads and armadillos. M. leprae is an obligate intracellular microorganism. This means that it must live within another cell to survive. In humans, it mainly infects macrophages and Schwann cells (part of peripheral nerves).
With the exception of cases from Armadillo transmission, the majority of cases are transmitted to those with close relatives with the infectious form of the disease who are living in the same home. It is highly unlikely that the disease would be transmitted from casual contact.
Most people who are exposed to leprosy do not develop disease. It is only those individuals with unique genetic and immunologic susceptibilities and significant exposures who will go on to develop clinical disease.
The clinical presentation of leprosy varies depending on the patient’s immunologic response to the infection. The clinical manifestations of leprosy are on a spectrum. On one end of the spectrum is tuberculoid leprosy in which the patient has a robust cell-mediated immune response to M. leprae. On the other end of the spectrum is lepromatous leprosy in which the patient has a poor cell-mediated immune response to the bacteria. Between the two ends of the spectrum are various intermediate presentations.
In tuberculoid leprosy the lesions are either few, usually five or less, or solitary. The distribution is asymmetric. The typical lesion will be a well-defined, hypopigmented, dry and hairless patch or plaque. Within the lesion the skin is anesthetic and there is an absence of sweating. The superficial nerves that serve the affected area may be thickened. The nerve damage may cause changes to the muscle groups served by the particular nerve.
In lepromatous leprosy there is much more extensive involvement compared to tuberculoid leprosy, reflecting a weaker immune response to controlling the organism. In this form of the disease there are diffuse and symmetrically distributed macules, papules, nodules and plaques most commonly involving the face, buttocks and lower extremities. When it affects the forehead the patient may develop “leonine facies,” in which the forehead and glabellar skin become thickened and give the appearance of a lion’s face. The earlobes may also become thickened.
Other signs include saddle nose due to collapse of the nasal cartilage and madarosis, which consists of loss of the lateral eyebrows. A glove and stocking anesthesia may develop resembling the peripheral neuropathy of diabetes. In severe cases there may be ocular involvement. In addition to the skin, eyes, and mucous membranes, the lymph nodes, bone marrow, liver, spleen and testicles may be infected.
The diagnosis is made clinically and by skin biopsy. In lepromatous disease, many mycobacterium will be seen within histiocytes — this is called multibacillary disease. In tuberculoid disease, no bacteria are visualized (paucibacillary) but there will be granulomas tracking along peripheral nerves.
In our case, leprosy was suspected by the anesthetic and hypopigmented patch of skin in a patient from a region of the world where leprosy is endemic. The diagnosis was confirmed by biopsy.
Treatment protocols vary depending on the type of leprosy. Any patient with multibacillary disease, those with more than five lesions, identified on biopsy should be treated with a multibacillary drug regimen. Patients with paucibacillary disease, those with five lesions or less, can be treated with a paucibacillary drug regimen. The treatment protocol in the United States differs from the protocol WHO recommends.
In the United States, patients with paucibacillary disease receive daily rifampin and dapsone for 12 months. Patients with multibacillary disease receive rifampin, dapsone and clofazamine for 24 months. WHO treatment protocols differ in order to provide shorter and less expensive therapy in regions where resources may be very limited. As an example, paucibacillary disease is treated with rifampin only once a month, along with daily dapsone for six months.
Adam Rees, MD, is a graduate of the University of California Los Angeles School of Medicine and a resident in the Department of Dermatology at Baylor College of Medicine in Houston.
- Bolognia J, Jorizzo JL and Rapini RP. “Chapter 74: Mycobacterial Infections.” Dermatology. St. Louis, MO: Mosby/Elsevier, 2008.
- James WD, Berger TG, Elston DM et al. “Chapter 17: Hansen’s Disease.” Andrews’ Diseases of the Skin: Clinical http://www.who.int/lep/en/Dermatology. Philadelphia: Saunders Elsevier, 2006.
- World Health Organization (WHO) n.d. Leprosy Elimination. Retrieved Feb. 27, 2013.