Lepra (leprosy) - Diagnosis

The diagnosis of leprosy is based on the identification of dermatological and neurological symptoms of the disease and the assessment of the results of functional and laboratory tests. Great importance is attached to the anamnesis, residence in an endemic zone, and contact with patients with leprosy. Since the patient has no subjective sensation of the disease for a long time (for years) (no fever, pain or itching in the area of the rash), it is necessary to examine the patient in good light for its timely detection. It is necessary to conduct a neurological examination to detect thickened nerve trunks and cutaneous nerve branches (especially in the area of the rash on the skin).

Minor's test is of great diagnostic value for assessing the sweating function. The skin area to be examined is lubricated with iodine solution and sprinkled with a thin layer of starch. Then the patient is made to sweat more (hot drink, dry-air bath, injection of 0.2 ml of 1% pilocarpine hydrochloride solution). In areas where there is no sweating, there will be no black color from the combination of iodine and starch in the presence of moisture.

The histamine test also has diagnostic significance. Due to the disturbance of peripheral neuroregulation in leprosy, the usual three-component skin reaction to histamine in the form of redness, swelling and itching may be either partial or completely absent.

The indicator of the body's immunological reactivity to leprosy infection is the lepromin test or Mitsuda reaction. Lepromin is a specially prepared suspension in an isotonic solution of leprosy mycobacteria taken from fresh leprosy of an untreated patient. With intradermal administration of 0.1 ml of lepromin, the result is read after 3 weeks. In healthy people and in patients with tuberculoid leprosy and borderline tuberculoid, the Mitsuda reaction is positive, and with a decrease or absence of resistance - negative.

The standard diagnostic procedure for leprosy includes:

• examination of the entire skin, as well as the mucous membranes of the upper respiratory tract;
• palpation of nerve trunks and cutaneous branches of nerves;
• examination of the limbs to detect amyotrophy and contractures:
• setting up functional tests in areas of skin lesions (detection of disturbances in various types of skin sensitivity, sweating test, nicotinic acid test, etc.):
• a bacterioscopic study that allows detection of acid-fast mycobacteria in smears from skin scarifications;
• pathohistological examination of skin taken from the edge of the lesion, with Ziehl-Neelsen staining to detect M. leprae.

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Indications for consultation with other specialists

Since leprosy, in addition to skin rashes, can also cause neurological and amyotrophic lesions, trophic ulcers and osteomyelitis, eye and respiratory lesions, patients are advised to consult a dermatologist, neurologist, surgeon, ophthalmologist, and otolaryngologist.

Patients with the lepromatous type of leprosy, as well as patients with borderline lepromatous and borderline forms of leprosy, related to bacteria excretors (open forms), should be hospitalized in anti-leprosy institutions according to epidemiological indications. It has been shown that after 3-6 months of active treatment they stop excreting bacteria into the environment. Patients with any other forms of leprosy in the acute stage of the process (reactive states) are also subject to hospitalization. Patients with tuberculoid forms of leprosy after diagnosis can undergo outpatient treatment (the issue of this and transfer to dispensary observation is decided by a commission of doctors of the anti-leprosy institution). Patients must adhere to the individual epidemic regimen prescribed to them; there are no other requirements for the regimen. The diet should be rich in proteins, contain a small amount of fat.

Differential diagnosis of leprosy

Differential diagnostics of leprosy is carried out with many diseases of the skin and peripheral nervous system: tubercular syphilid, syphilitic gummas, toxicoderma, multiform exudative erythema, lichen planus, tuberculosis of the skin, sarcoidosis, mycosis fungoides, reticulosis, leishmaniasis, nodular erythema, trophic and perforating ulcers of the feet of various etiologies, etc. The tuberculoid type of leprosy is indicated by the nature of the rash and the violation of superficial types of sensitivity in them (sometimes - the detection of single M. leprae during histological examination). A verifying sign for the lepromatous type of leprosy, in addition to clinical symptoms, is the detection of a large number of M. leprae.

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