What is Leprosy?

Leprosy is a chronic infectious disease caused by Mycobacterium leprae.
It affects mainly the peripheral nerve skin and occasionally the eyes.
Of all the communicable disease, Leprosy is most important for its potential to cause permanent and progressive physical disability. It is associated with social stigma because of the deformities it may produce in a good number of patients.

How does it spread?

Man is the only known source for M leprae
It is transmitted from one untreated multi-bacillary patient to another person via the respiratory tract or skin. The major sites from which bacilli escape from the body of an infectious patient are the nose and mouth.
Nose appears to be the major site of entry of the bacilli.

How a case of Leprosy is diagnosed?

Diagnosis of Leprosy?

A case of Leprosy is diagnosed by eliciting cardinal sign of Leprosy through clinical and pathological examination (bacteriological and histopathological examination)

Clinical Examination

Clinical examination includes careful interview of patients to get detailed history and skin and nerve examination.

Ziehl-Neelsen method of starting M.laprae in smears

There are many minor modifications of this method, each as good as another in the hands of an experienced technician, and the method described here is a reliable guide:

  • The slide with the smear on it should be covered with carbol fuchsin and heat applied beneath it, either with a gas flame (Bunsen burner) or with a sprit lamp. Heating should be sufficient to cause stream to rise from all parts of the slide, but boiling is avoided. The slide should be left for 15 minutes without any further heating.
  • The stain is tipped away and the slide is held under a gentle stream of water.
  • Pour acid- Alcohol mixture on to the slide and leave for 3 seconds if the smear is thin or for 5 seconds if the smesr is thick, then washes it away with running water. The acid-alcohol mixture consists of 1% hydrochloric acid in 70% alcohol. The slide is inspected to see the degree of pink less; if faintly pink proceed to the next stage, but if deeply pink treat again with acid-alcohol for 2 seconds and wash with running water.
  • Cover the slide with counter-strain, such as 1% methylene blue for about 10 seconds.
  • Wash in running water and allow to dry.

Bacterial indices

It should be noted that M. leprae,incommon with other mycobacteria, retains the property of staining with carbol fuchsin when no longer alive, therefore, a technician examining skin smears during treatment will get the impression that the patient is making no progress unless he can differentiate leaving form death bacilli. The morphology or structure of the bacilli seen after Ziehl- Neelsen staining is all important, seen living bacilli appears uniformly stained rods (solid staining) and dead bacilli appear irregularly stained (fragmented bacilli) or as granules(granular bacilli) (plate 2). The density of bacilli in smears is known as the bacterial (bacteriological) index (BI) and includes both living and dead bacilli. It can be recorded in a number of ways, the simplest being a system recorded many bacilli (+ + +) moderate numbers (+ +), few (+), no bacilli (-) but if a more comprehensive system is desired, redley; s logarithmic scale4 is recommended. This is based on the number of bacilli seen in a average microscopic field using an oil immersion objective (1/2 in or 2 mm).

6+ Many clumps of bacilli in an average field (over 1000).
5+ 100-1000 bacilli in an average field.
4+ 10-100 bacilli in an average field.
3+ 10-100 bacilli in an average field.
2+ 1-10 bacilli in 10 fields.
1+ 1-10 bacilli in 10 fields.

Cardinal symptoms of Leprosy

Hypo pigmented or radish or cupper color skin lesion with definite loss of sensation
Involvement of the peripheral nerve (thickening and tenderness) with
loss of sensation and weakness of the muscles of hands feet and face.
Presence of Mycobacterium laprae of slit skin smear if taken from the lesion and nasal smear.

Skin examination

How the skin is examined?

1. A spot where good light is available should be chosen.
2. A place where there is privacy should be selected.
3. Skin of all parts starting from head to toe should be examined.

Nerve Examination

Examination of nerve of all the patients is VERY IMPORTAINTS for diagnosis and prevention of disability. This involves two aspects

Palpation of nerve thickening, Tenderness and consistent
Assessment of nerve function.

when palpating the nerve, you should look for three things – Thickening, Tenderness and consistency
always palpates across the course the nerve
Palpates the nerve gently with the pulp of the finger, not the tip
Lool at the patient face while palpating the nerve to elicit tenderness
Always compare both sides to assess thickness and consistency.


Cardinal signs that help in diagnosing Leprosy are

1. Hypopigmented or reddish skin lesions with definite loss of sensation
2. Involvement of peripheral nerve as demonstrated definite thickening with loss of sensation and weakness of the muscles of the hand and feet.
3. One should examine the patches in the skin for site number color infiltration and sensory loss. These characteristics help in diagnosis of disease, reaction and classification

What is the disability seen in a Leprosy Patient

Leprosy is associated with intense stigma because of the disabilities and deformities that result from Leprosy. Most of the disability that occurs in Leprosy is preventable therefore it is very important to prevent the disability from occurring.
Damaged to peripheral nerves supplying the hands and the feet and results in loss of sensation over the area supplied by the nerve and paralysis of the muscles supplied by the nerve.

Loss of sensation, sweating and paralysis can lead to wounds, skin cracks and stiffness of the joints may occur, if the patients neglect his hand and feet. Ultimately this can lead to loss of bone and tissue of the limbs and severe deformity