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Chapter: Medical Microbiology: An Introduction to Infectious Diseases: Mycobacteria

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Leprosy : Clinical Aspects

Two major forms of the disease are recognized, tuberculoid and lepromatous. However, intermediate forms occur, and the first form may merge into the second.

LEPROSY : CLINICAL ASPECTS

MANIFESTATIONS

Two major forms of the disease are recognized, tuberculoid and lepromatous. However, intermediate forms occur, and the first form may merge into the second.

Tuberculoid Leprosy

Tuberculoid leprosy involves the development of macules or large, flattened plaques on the face, trunk, and limbs, with raised, erythematous edges and dry, pale, hairless centers. When the bacterium has invaded peripheral nerves, the lesions are anesthetic. The disease is indolent, with simultaneous evidence of slow progression and healing. Because of the small number of organisms present, this form of the disease is usually noncontagious.

Lepromatous Leprosy

In lepromatous multibacillary leprosy, CMI is deficient, and patients are anergic to lep-romin. Growth of M. leprae is, thus, relatively unimpeded. Histologically, lesions show dense infiltration with leprosy bacilli, and large numbers may reach the bloodstream. Skin lesions are extensive, symmetric, and diffuse, particularly on the face, with thickening of the looser skin of the lips, forehead, and ears, resulting in the classic leonine appearance. Damage may be severe, with loss of nasal bones and septum, sometimes of digits, and with testicular atrophy in men. The organism spreads systemically, with involvement of the reticuloendothelial system.

DIAGNOSIS

Laboratory diagnosis of lepromatous leprosy involves preparation of acid-fast stained scrap-ings of infected tissue, particularly nasal mucosa or ear lobes. Large numbers of acid-fast bacilli are seen. Tuberculoid leprosy is diagnosed clinically and by histologic appearance of full-thickness skin biopsies. PGL-1 – based serologic tests have been evaluated for their use-fulness in serodiagnosis. The specificity has been excellent, but the sensitivity for tubercu-loid leprosy is still unsatisfactory. It is likely that suitable serologic tests will be available for this disease in the near future.

TREATMENT AND PREVENTION

Treatment has been revolutionized by the development of sulfones, such as dapsone, which blocks para-aminobenzoic acid metabolism in M. leprae. When combined with rifampin, dapsone usually controls or cures tuberculoid leprosy when given for 6 months. In lepromatous leprosy and multibacillary intermediate forms of the disease, a third agent (clofazimine) is added to help prevent the selection of resistant mutants, and treatment is continued at least 2 years. Prevention of leprosy involves recognition and treatment of infectious patients and early diagnosis of the disease in close contacts. Chemoprophylaxis with sulfones has been used for children in close contact with lepromatous cases. Immunization with BCG vaccine has been investigated, with varying results.

A possible diagnosis of leprosy elicits fear and distress in patients and contacts out of all proportion to its risks. Few clinicians in the United States have the experience to make such a diagnosis, and expert help should be sought from public health authorities before reaching this conclusion or indicating its possibility to the patient.

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