Laboratory diagnosis of leprosy

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laboratory diagnosis of leprosy

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Laboratory diagnosis of leprosy

  1. 1. LABORATORY DIAGNOSIS OF LEPROSY T. ARUVI II MBBS
  2. 2. LEPROSY • Leprosy, also known as Hansen's disease (HD), is a chronic infection caused by the bacteria Mycobacterium leprae and Mycobacterium lepromatosis. • It is primarily a granulomatous disease of the peripheral nerves and mucosa of the upper respiratory tract; skin lesions are the primary external sign.
  3. 3. DIAGNOSIS OF LEPROSY • Diagnosis of leprosy is most commonly based on the clinical signs and symptoms. • Only in rare instances is there a need to use laboratory and other investigations to confirm a diagnosis of leprosy. • In an endemic country or area, an individual should be regarded as having leprosy if he or she shows ONE of the following cardinal signs: o skin lesion consistent with leprosy and with definite sensory loss, with or without thickened nerves o positive skin smears
  4. 4. • For patients presenting the above symptoms, a leprosy diagnosis is confirmed after analysis of tissues biopsied from infected sites. • Typically, a stain for acid-fast bacteria is performed . • Additional steps may include culturing infected tissue to confirm other bacteria are not involved - M. leprae cannot be culture in vitro using PCR amplification to verify the presence of DNA specific to M. leprae.
  5. 5. PHOTOMICROGRAPH DEPICTING AN ACID FAST STAIN OF MYCOBACTERIUM LEPRAE BACTERIA.
  6. 6. SAMPLE COLLECTION FROM SKIN LESION • Specimen are collected from nasal mucosa, skin lesion and clear lobules. • Blunt, narrow scalpel is introduced into the nose and a piece of mucous membrane is taken. – NASAL MUCOSA • Skin is pinched and cut about 5mm and a deep infiltrated layer is taken with a scalpel. – SKIN LESION
  7. 7. A PHOTOMICROGRAPH OF MYCOBACTERIUM LEPRAE TAKEN FROM A LEPROSY SKIN LESION.
  8. 8. OTHER TESTS • Lepromin skin test : • Although not diagnostic of exposure to or infection with M leprae, this test assesses a patient's ability to mount a granulomatous response against a skin injection of killed M leprae. • Patients with tuberculoid leprosy or borderline lepromatous leprosy typically have a positive response (>5 mm). • Patients with lepromatous leprosy typically have no response.
  9. 9. • Polymerase chain reaction (PCR): • PCR and recombinant DNA technology have allowed for the development of gene probes with M leprae –specific sequences. • This technology can be used to identify the mycobacterium in biopsy samples, skin and nasal smears, and blood and tissue sections. • Lymphocyte migration inhibition test (LMIT): • As determined by a lymphocyte transformation and LMIT, cellmediated immunity to M leprae is absent in patients with lepromatous leprosy but present in those with tuberculoid leprosy. • Contact or family screening for history of leprosy
  10. 10. PCR DETECTION OF M. LEPRAE DNA IN BIOPSY SAMPLES FROM LEPROSY PATIENTS.

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