Leprosy is a chronic infectious disease caused by Mycobacterium leprae.
An individual should be regarded as having leprosy if he or she shows ONE of the following cardinal signs:
The skin lesion can be single or multiple, usually less pigmented than the surrounding normal skin. Sometimes the lesion is reddish or copper-coloured.
A variety of skin lesions may be seen but macules (flat), papules (raised), or nodules are common. Sensory loss is a typical feature of leprosy.
The skin lesion may show loss of sensation to pin pick and/or light touch. Thickened nerves, mainly peripheral nerve trunks constitute another feature of leprosy.
A thickened nerve is often accompanied by other signs as a result of damage to the nerve. These may be loss of sensation in the skin and weakness of muscles supplied by the affected nerve.
In the absence of these signs, nerve thickening by itself, without sensory loss and/or muscle weakness is often not a reliable sign of leprosy.
Positive skin smears: In a small proportion of cases, rod-shaped, red-stained leprosy bacilli, which are diagnostic of the disease, may be seen in the smears taken from the affected skin when examined under a microscope after appropriate staining.