Health Significance Of The Clinical Pathology Of Leprosy (Hepatic Disorders)

Funom MakamaStarred Page By Funom Makama, 20th Mar 2014 | Follow this author | RSS Feed | Short URL http://nut.bz/3x6ua95f/
Posted in Wikinut>Health>General Health>Diseases & Infections

The organisms multiply in the nervous tissue, skin and upper respiratory tract mucosa. During the early stages of infection the clinical and histological changes are non-specific. The dermal nerve twigs show infiltration with round cells and histiocytes.

Pathology Of Leprosy

Mycobacteria may be seen in nerves and muscles of the skin and this is diagnostic. This stage is known as the indeterminate stage since it is not possible to predict the clinical outcome at this stage. The lesion heals due to natural resistance in 75% of cases. In those with progression of lesions tuberculoid lesions develop in the presence of good immunity whereas lepromatous lesions develop in its absence.

Tuberculoid Leprosy

This type is characterized by well localized granulomatous lesions in and around the nerves. The cells are derived by the mobilization of phagocytic macrophages which are transformed into epitheloid and giant cells. These are surrounded by lymphocytic infiltration. This granuloma extends into the epidermis. The dermal nerves are destroyed by cellular infiltration. Caseation is rarely seen in the nerves. The bacilli are very few and are not generally demonstrable in these lesions. Such patients are non-infective.

Lepromatous Leprosy

Mononuclear phagocytes ingest the organisms which multiple within and fill them completely. These bacterial masses are called globi and such cells are called lepra cells. Their cytoplasm is foamy. Lymphocytes are only a few or absent. There is no attempt at tubercle formation. The dermis is infiltrated throughout its entire thickness. The nerves, erector pill muscles and endothelial lining of blood vessels also show similar changes. The epidermis is spared and a clearcell free zone exists below the epidermis. The organisms are disseminated through the blood stream to the other parts of the skin and organs such as eyes, respiratory mucosa, testes, liver, kidneys and muscles of the hands, feet and face. As a later complication amyloidosis may develop.

Borderline Leprosy

When the immunity is variable, borderline leprosy develops in which the histologicaly picture tends to vary. With good cell-mediated immunity, the picture resembles tuberculoid leprosy and this case is called ‘boderline tuberculoid’ (BT). There is differentiation of mononuclear phagocytes into epithelioid cells, but giant cells are not common. Lymphocytes are usually present but do not show tubercle formation. The subepidermal zone is clear. Nerves are infiltrated but are still recognizable.

When the immunity wanes, the picture resembles that of lepromatous leprosy and this case is called ‘boderline lepromatous’ (BL). In peripheral neuropathy occurring in leprosy, the nerves are damaged mainly by the cellular reaction to the components of dead bacilli.

The Lepromin Test

The lepromin test is a skin test which detects delayed hypersensitivity (Mitsuda 1919). Originally, the antigen (lepromin) was prepared from boiled emulsified bacilli. It is injected intradermally. This results in a biphasic reaction consisting of two separate events. The first (Fernandez reaction) consists of erythema and induration which develops in 24 to 48 hours and remains so for 3 to 5 days. This is analogous to tuberculin reaction. The second is (Mitsuda reaction) appears in 3 weeks, reaches a peak in 4 weeks and subsides after a few weeks. The skin becomes indurated and may ulcerate. This later reaction is taken to indicated lepromin positivity. Several modifications have been made in the preparation of the antigen.

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author avatar Funom Makama
22nd Mar 2014 (#)

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