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Leprosy in Adult
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Leprosy in Adult

Contributors: T. P. Zulu BSc, MBChB, MMed, FCDerm, Natal, Anisa Mosam MBChB, MMed, FCDerm, PhD, Ncoza C. Dlova MBChB, FCDerm, PhD, Susan Burgin MD
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Leprosy, also known as Hansen disease, is a chronic granulomatous infection caused by Mycobacterium leprae (Hansen's bacillus), an acid-fast mycobacterium. Leprosy is endemic in the Middle East, India, Southeast Asia, Africa, the Pacific basin, Mexico, Central America, and South America. Sporadic cases have been reported in the southern United States, Spain, and Portugal. However, 83% of all cases come from 6 countries: Brazil, Nepal, India, Burma, Indonesia, and Madagascar.

Leprosy is classified into 5 disease types based on clinical, immunologic, and pathologic criteria:
  • Tuberculoid leprosy (TT)
  • Borderline tuberculoid leprosy (BT)
  • Midborderline leprosy (BB)
  • Borderline lepromatous leprosy (BL)
  • Lepromatous leprosy (LL)
These disease types represent a spectrum of disease activity, with tuberculoid leprosy representing intact cell-mediated immunity at one end of the spectrum, lepromatous leprosy representing poor immune response to M. leprae at the other end of the spectrum, and 3 stages of intermediate immune response. Patients with lepromatous leprosy are the most contagious. Diffuse lepromatous leprosy occurs when the entire cutaneous surface is involved. Histoid leprosy is a very rare variant of lepromatous leprosy that presents with papules and nodules.

Transmission of leprosy is still not completely understood. The average incubation period for M. leprae is about 5 years, with a range from 2 to over 30 years. Leprosy in returning tourists or travelers is exceedingly rare.

Mycobacterium leprae has a predilection for the cooler parts of the body, skin, peripheral nerves, upper respiratory system, anterior eye chambers, and testes. Peripheral neuropathy may occur across the spectrum before, during, and after treatment. Small nerve fibers conveying fine touch, temperature, and pain sensations are the most impaired. During immune exacerbations (reactions), fever, arthralgias, neuritic pain, uveitis, and orchitis may occur.

Mycobacterium lepromatosis is a newly identified mycobacterium that usually causes diffuse lepromatous or lepromatous leprosy. The significance of infection with M. lepromatosis is still not clearly understood.


A30.9 – Leprosy, unspecified

81004002 – Leprosy

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Differential Diagnosis & Pitfalls

Hypopigmented patches:
Erythematous macules:
Isolated plaques:
Infiltrative plaques:
Histoid leprosy clinically simulates:

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Last Reviewed:12/14/2017
Last Updated:12/14/2017
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Leprosy in Adult
Leprosy (Tuberculoid Leprosy) : Numbness/tingling, Chronic duration lasting years, Foot drop, Hypopigmented patch, Neuropathy peripheral, Paresthesias, Annular configuration
Clinical image of Leprosy
Numerous reddish-brown plaques and nodules on the arm.
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