Laboratory diagnosis of leprosy is primarily based on clinical signs and symptoms. Skin and nasal smears can be taken from lesions to look for acid-fast Mycobacterium leprae bacteria under microscopy. Biopsies of infected skin or nasal tissue can also be analyzed with acid-fast staining, culturing, or PCR to confirm the presence of M. leprae DNA. Classification of leprosy type is aided by the Lepromin skin test response and lymphocyte proliferation assays, which indicate level of cell-mediated immunity toward M. leprae.

1. LABORATORY DIAGNOSIS
OF LEPROSY
T. ARUVI
II MBBS

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. 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. • 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. PHOTOMICROGRAPH DEPICTING AN ACID
FAST STAIN OF MYCOBACTERIUM LEPRAE
BACTERIA.

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. A PHOTOMICROGRAPH OF
MYCOBACTERIUM LEPRAE TAKEN FROM A
LEPROSY SKIN LESION.

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. • 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. PCR DETECTION OF M. LEPRAE DNA IN
BIOPSY SAMPLES FROM LEPROSY PATIENTS.