Leprosy: a primer for Canadian physicians

Abstract

Leprosy is a rare but serious infectious disease caused by Mycobacterium leprae. While global prevalence of the disease is decreasing, increasing rates of immigration from countries where leprosy is endemic have led to the recognition of this illness in North America. Classically, leprosy presents as hypopigmented cutaneous macules along with sensory and motor peripheral neuropathies, although the clinical manifestations vary along a disease spectrum. In addition to primary infection, patients may undergo a "reaction," an acute inflammatory response to the mycobacterium, which leads to pain and erythema of skin lesions and dangerous neuritis. Reactions can occur at any time during the course of leprosy, but they tend to be precipitated by treatment. They are a significant cause of impaired quality of life due to marked nerve damage and thus warrant prompt intervention. Although leprosy may have a protracted onset and be difficult to recognize, cure is achievable with appropriate multidrug therapy. Because untreated leprosy can result in permanent, irreversible nerve damage and secondary transmission, early diagnosis and treatment are essential to minimize morbidity.

Fig. 1: Clinical spectrum of leprosy. CMI = cell-mediated immunity, TT = tuberculoid leprosy, BT = borderline tuberculoid leprosy, BB = borderline leprosy, BL = borderline lepromatous leprosy, LL = lepromatous leprosy.

Fig. 2: Clinical signs associated with leprosy in various stages of the disease. A: Large hypopigmented macule of TT leprosy. B: BL leprosy. C: BB leprosy before therapy. D: The same patient as in Fig. 2C undergoing a type I reversal reaction during therapy. Note the accentuation and erythema of macules relative to Fig. 2C. E: Patient with BT leprosy undergoing a type I reversal reaction. F: Patient with LL leprosy undergoing a type II reaction (erythema nodosum leprosum). Note the raised, erythematous crops of nodules.