Answer: Can you identify this condition?

3. Tuberculoid leprosy

This case demonstrates the need for family physicians to take a closer look at insensate lesions and consider leprosy in the differential. Leprosy has potentially disfiguring and disabling sequelae. It is underdiagnosed in nonendemic areas, so it is not surprising that the diagnosis was missed by multiple physicians in this case.

Leprosy is a chronic granulomatous infection caused by Mycobacterium leprae; it predominantly affects the skin and the peripheral nervous system.1 Transmission occurs via the nasal discharge of infected lepromatous (LL) individuals. Incubation is very long, averaging 2 to 5 years for tuberculoid (TT) disease and 8 to 12 years for LL disease.2 Leprosy has infected or disabled an estimated 4 million people worldwide. In 1991 the World Health Organization passed a resolution to eliminate leprosy as a public health concern; since then, the prevalence of the disease has decreased by about 90%. Most newly reported cases occur in India, Brazil, and Indonesia, but a number of other East-Asian and African countries are noteworthy contributors.3

Five subtypes of leprosy comprise the spectrum of the disease: TT, borderline tuberculoid (BT), borderline (BB), borderline lepromatous (BL), and LL. These classifications might not apply in the early stages, when indeterminate leprosy is recognized.4 The main features of the subtypes are summarized in Table 1.4

Presentation depends on an individual’s degree of cell-mediated immunity (CMI) toward M leprae. High levels of CMI result in the TT form of the disease, in which the body is able to contain the infection to a single or a few sites. On the other hand, lack of CMI means the bacteria can multiply and disseminate throughout the body, resulting in the widespread disease found in LL. Borderline classes of leprosy describe the disease within the continuum of an individual’s CMI response. Other variants of leprosy exist, however, including indeterminate, pure neuritic, histoid, and Lucio leprosies.2

Diagnosis

Diagnosis of leprosy requires demonstration of acid-fast bacilli in skin lesions or can be made clinically based on 2 of the following 3 signs2:

• anesthesia of the skin lesion, the distribution of a peripheral nerve, or the dorsal surfaces of the hands or feet;

• thickened nerves, especially posterior tibial, ulnar, median, lateral popliteal, facial, and peripheral nerve trunks; and

• typical skin lesions.

The lepromin test (analagous to the tuberculin test used in tuberculosis) is performed by intradermal injection of a heat-killed preparation of M leprae bacilli. It is not used in clinical practice because of its low sensitivity.5

Subtypes of leprosy have varying presentations:

Natural course

Fluctuations in the host immune response to leprosy lead to “reactions,” which can be an important source of morbidity (Table 2).* They usually occur during the first few months of treatment or can be precipitated by pregnancy, concomitant infection, and other triggers.

In long-standing leprosy, without treatment, nerve damage leads to anesthesia, muscle weakness, joint contractures, and autonomic dysfunction. Inadvertent trauma due to anesthesia can lead to cellulitis, osteomyelitis, disfigurement, and severe disability (Figure 2). Blindness from ocular involvement is one of the more dreaded sequelae.6,7

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Figure 2

Sequelae of long-standing leprosy without treatment

Treatment

Multidrug therapy is recommended because M leprae is highly resistant. Medications for leprosy are covered by the World Health Organization as part of the worldwide eradication program. Regimens for TT (paucibacillary) leprosy include monthly doses of rifampin along with daily doses of dapsone for 6 months, and follow-up scheduled after 2 years. Lepromatous lesions are treated with a combination of rifampin, dapsone, and clofazimine for 12 months and are followed for 5 years.2,3

In addition to pharmacotherapy, patients must be educated on how to reduce the risk of injury from sensory impairment. Patients might also experience psychological symptoms due to the social stigma attached to the diagnosis; therefore, appropriate support should be considered.