• Leprosy, also known as Hansen's disease
(HD), is a chronic infection caused by the
bacteria Mycobacterium leprae and
• It is primarily a granulomatous disease of
the peripheral nerves and mucosa of the
upper respiratory tract; skin lesions are the
primary external sign.
DIAGNOSIS OF LEPROSY
• Diagnosis of leprosy is most commonly based on the clinical signs and
• 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
o positive skin smears
• For patients presenting the above symptoms, a leprosy
diagnosis is confirmed after analysis of tissues biopsied from
• 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
PHOTOMICROGRAPH DEPICTING AN ACID
FAST STAIN OF MYCOBACTERIUM LEPRAE
SAMPLE COLLECTION FROM SKIN
• Specimen are collected from nasal mucosa, skin lesion and clear
• 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
A PHOTOMICROGRAPH OF
MYCOBACTERIUM LEPRAE TAKEN FROM A
LEPROSY SKIN LESION.
• 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.
• 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
• 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
PCR DETECTION OF M. LEPRAE DNA IN
BIOPSY SAMPLES FROM LEPROSY PATIENTS.