laboratory diagnosis of leprosy
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laboratory diagnosis of leprosyTRANSCRIPT
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LABORATORY DIAGNOSIS OF LEPROSYT. ARUVI
II MBBS
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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.
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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
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• 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.
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PHOTOMICROGRAPH DEPICTING AN ACID FAST STAIN OF MYCOBACTERIUM LEPRAE
BACTERIA.
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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
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A PHOTOMICROGRAPH OF MYCOBACTERIUM LEPRAE TAKEN FROM A
LEPROSY SKIN LESION.
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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.
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• 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, cell-
mediated 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
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PCR DETECTION OF M. LEPRAE DNA IN BIOPSY SAMPLES FROM LEPROSY PATIENTS.
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