Tb lymphnode, tuberculoid and lepromatous leprosy

TB LYMPHNODE, TUBERCULOID AND

LEPROMATOUS LEPROSY

-Dr Sowmya Srinivas

INTRODUCTION When circulating blood reaches the capillaries, part of its fluid

content passes into the surrounding tissues as tissue fluid. Most of this fluid re-enters the capillaries at their venous ends. Some of it is, however, returned to the circulation through a

separate system of lymphatic vessels (usually called lymphatics).

The fluid passing through the lymphatic vessels is called lymph.

The largest lymphatic vessel in the body is the thoracic duct. The thoracic duct ends by joining the left subclavian vein at its

junction with the internal jugular vein. On the right side there is the right lymphatic duct that has a

similar termination.

Scattered along the course of lymphatic vessels there are numerous small bean-shaped structures called lymph nodes that are usually present in groups.

As a rule lymph from any part of the body passes through one or more lymph nodes before entering the blood stream.

Lymph nodes act as filters removing bacteria and other particulate matter from lymph.

Lymphocytes are added to lymph in these nodes.

NORMAL HISTOLOGY The lymph node has an outer zone that contains

densely packed lymphocytes, and therefore stains darkly: this part is the cortex.

Surrounded by the cortex, there is a lighter staining zone in which lymphocytes are fewer: this area is the medulla.

Within the cortex there are several rounded areas that are called lymphatic follicles or lymphatic nodules.

Each follicle has a paler staining germinal centre surrounded by a zone of densely packed lymphocytes.

TB LYMPH NODE Its the most frequent presentation of

extrapulmonary tuberculosis, usually occurring in the cervical region (“scrofula”).

In HIV-negative individuals, lymphadenitis tends to be unifocal and localized.

HIV-positive people, on the other hand, almost always have multifocal disease, systemic symptoms, and either pulmonary or other organ involvement by active tuberculosis.

GROSS FEATURES Large multinodular mass that resembles

carcinoma with multiple foci of caseous necrosis.

TUBERCULOUS LYMPHADENITIS Its a chronic specific granulomatous

inflammation with caseation necrosis. The characteristic morphological element is

the tuberculous granuloma (caseating tubercule) : giant multinucleated cells (Langhans cells), surrounded by epithelioid cells aggregates, T cell lymphocytes and few fibroblasts.

Granulomatous tubercules evolve to central caseous necrosis and tend to become confluent, replacing the lymphoid tissue.

TUBERCULOUS GRANULOMA Multinucleated giant cell : 50 - 100 microns, numerous

small nuclei (over 20) disposed at the periphery of the cell (crown or horseshoe), abundant eosinophilic cytoplasm.

Epithelioid cells are activated macrophages resembling epithelial cells : elongated, with finely granular, pale eosinophilic (pink) cytoplasm and central, ovoid nucleus.

At the periphery are the lymphocytes (T cells) and rare plasma cells and fibroblasts.

Caseous necrosis is a central area, amorphous, finely granular, eosinophilic (pink).

LEPROSY Leprosy (lepra) is a chronic infection caused by

Mycobacterium leprae. It affects mainly the skin, nasal mucosa, and peripheral nerves.

Mycobacterium leprae is an obligate, intracellular, gram-positive organism that is also acid fast, although less so than M. tuberculosis.

Mycobacterium leprae is found predominantly in three main cell types in the skin: Schwann cells, endothelial/perithelial cells, and cells of the monocyte-macrophage system

RIDLEY–JOPLING CLASSIFICATION Tuberculoid Leprosy (TT) Borderline-tuberculoid (BT) Borderline (BB) Borderline-lepromatous (BL) Lepromatous Leprosy (LL)

SIGNS AND SYMPTOMS Its a systemic disease, although the primary

clinical manifestations are in the skin. Mucosal involvement may lead to ulceration of

the nasal septum. Nerve lesions may result in acral anaesthesia,

claw hand, and foot drop. The cutaneous lesions, which are usually

symmetrical, include multiple small macules, infiltrated plaques, and nodules with poorly defined borders.

MICROSCOPY Tuberculoid leprosy: Epithelioid histiocytes surround small

cutaneous nerves Langerhans giant cells may be seen but

without necrosis. Bacilli are usually scarce

LEPROMATOUS LEPROSY Has collections and sheets of heavily

parasitized macrophages within the dermis, with a sparse sprinkling of lymphocytes

Rarely, subcutaneous and deep dermal inflammatory nodules are present.

In older lesions, the macrophages have a foamy appearance (lepra cells, Virchow cells).

Numerous acid-fast bacilli are present in macrophages, sweat glands, nerves, Schwann cells, and vascular endothelium.

THANK YOU [email protected]