Clinical Testing and Diagnosis for Leprosy (Hansen's disease)

Key points

  • Leprosy is diagnosed based on clinical presentation, and the diagnosis is confirmed by skin or nerve biopsy and acid-fast staining.
  • In the United States, the National Hansen’s Disease Program can provide diagnostic services.
  • Leprosy s a reportable condition to state or local health departments.

Arranging diagnostic testing

In the United States, the National Hansen’s Disease Program can provide diagnostic services.

Healthcare providers should seek prompt consultation with National Hansen's Disease Program. Phone 1-800-642-2477, weekdays 9 AM to 5:30 PM ET (in Hawaii: 1-808-733-9831).

Recommended specimens

Depending on the form of leprosy the treating physician suspects, the following specimens may be collected:

  • Skin smears from the earlobes, elbows, and knees
  • Skin biopsy from edges of active patches
  • Nerve biopsy from thickened nerves

Recommended tests

Skin and nerve biopsy

Biopsies are needed to definitively diagnose and classify leprosy. Slit skin smear may also be helpful in diagnosing those with multibacillary (MB) leprosy.

In MB leprosy, biopsying tissue from various affected sites may reveal typical histopathologic changes and large numbers of foam cells. Foam cells are macrophages that have ingested M. leprae or M. lepromatosis bacteria but are unable to digest the organisms. The M. leprae bacteria multiply and use the macrophage as a method of transport throughout the body. This is how the bacteria cause the multiple lesions that appear in all parts of the body on MB leprosy patients.

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This photomicrograph shows a red circle indicative of the classic histopathologic changes found in a skin section from an individual with leprosy.
This photomicrograph shows classic histopathologic changes in a skin section from someone with leprosy. A nerve is surrounded by a dense infiltrate of undifferentiated histiocytes and large numbers of lymphocytes. The nerve sheath and endoneural region of the nerve were also infiltrated. This neural involvement was found to be independent of any pathology of the upper corium.
This photomicrograph is shows abnormally shaped cells and reveals some of the histopathologic changes in a specimen of human testicular tissue
This photomicrograph reveals some of the histopathologic changes in a specimen of human testicular tissue, which included a large number of “foam cells”. These changes were attributed to a case of MB leprosy.

Acid-fast staining

Laboratory workers should use the Ziehl-Neelson method using 5% sulfuric acid as decolorizing agent. The presence of acid-fast bacilli confirms the diagnosis of leprosy.

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This photomicrograph of a skin tissue sample from a patient with Hansen's disease shows a cutaneous nerve, which had been invaded by numerous M. leprae bacteria (shown in red).
A photomicrograph of a skin tissue sample shows a cutaneous nerve, which had been invaded by numerous M. leprae bacteria (shown in red).
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This acid-fast-stained photomicrograph of a tissue sample extracted from a patient with leprosy shows a chronic inflammatory lesion known as a granuloma, within which numerous red-colored M. leprae bacteria are visible.
This acid-fast-stained photomicrograph of a tissue sample shows a granuloma, within which many red-colored M. leprae bacteria are visible.

Polymerase Chain Reaction (PCR) Testing

PCR testing can detect genetic material from M. leprae and M. lepromatosis in a skin biopsy. PCR may be useful when clinical and histopathologic findings are unclear. PCR does not replace routine diagnostic methods but can provide supportive evidence for leprosy, particularly in early or paucibacillary cases. PCR testing for leprosy is available only in specialized laboratories, including the National Hansen's Disease Program.

Reporting cases

Leprosy cases must be reported to jurisdictions when identified by a healthcare provider, hospital, or laboratory. Specific reporting requirements may vary by jurisdiction.

For Public Health Hansen's Disease Case Definition, Reporting, and Surveillance
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Content Source:
National Center for Emerging and Zoonotic Infectious Diseases (NCEZID)