The lymphatic system is a network of organs and tissues whose main function is to help us defend ourselves against infections. It consists of lymph nodes, lymphatic vessels and the lymphoid organs. The lymph nodes are found all over the body. Their function is to filter the lymph. The lymph nodes are connected to the lymphatic vessels, which convey lymph to and away from the lymph node. The lymphoid organs are the thymus and spleen. Thymus is the site where immature T lymphocytes come after leaving the bone marrow, and reach maturity. The spleen is the largest lymphoid organ. It performs many functions, such as filtering blood and removing old red blood cells from the circulation.

Lymphadenopathy

Lymphadenopathy is a disease which is characterised by the inflammation of the lymph nodes. This inflammation can be localised to only some nodes or can be generalized. Usually, a localized inflammation of lymph nodes is due to an infection, foreign particles, or other diseases of organs that are situated close to them. Lymph nodes inflamed due to an infection tend to be painful, but those inflamed from cancers are usually painless.

Enlarged lymph nodes at a particular site are often associated with certain diseases. Axillary lymph nodes can get affected by infections or cancers of the hand, breast and chest region. Supraclavicular lymph nodes can get affected by diseases of the lungs, oesophagus and thorax. Inguinal lymph nodes are connected to the lower abdominal region, external reproductive structures, perineum and lower anal region. Diseases of any of these organs can have an impact on the inguinal lymph nodes. Bilateral hilar lymphadenopathy (BHL) occurs when mediastinal lymph nodes are affected. This is a major feature of the disease, sarcoidosis. Likewise, whichever group of nodes is connected to a particular region, it is affected by diseases of that region. Generalized lymphadenopathy, involving the lymphatic system of the whole body, can occur due to HIV infection, tuberculosis and cancers of the lymphatic system.

Many diseases have lymphadenopathy as a secondary complication. Some such factors are:

• Pathogenic Organisms: Infection by various bacteria, viruses, fungi and other organisms can cause inflammation of the lymph nodes. Bacteria (Staphylococci, Streptococci, Mycobacteria, Brucella, etc.), viruses (HIV, Epstein-Barr virus, etc.), fungi (Histoplasma, Coccidioides, etc.), and other organisms like Toxoplasma gondii and Leishmania, commonly cause infections that affect lymph nodes.
• Other Causes: Cancers of the lymphoid system or cancers that have originated in a part of the body and metastasised to other locations may cause lymphadenopathy. Other diseases that have lymphadenopathy as a complication are sarcoidosis, rheumatoid arthritis and amyloidosis. Some drugs such as phenytoin can also cause lymph node inflammation.

Lymphoma

Cancers of the lymphoid tissues are referred to as lymphomas. They are grouped into two broad types, known as Hodgkin's lymphoma and Non-Hodgkin's lymphomas, based on a feature that distinguishes the two from each other. That criterion is the presence of a type of large cell, known as Reed-Sternberg cell, in Hodgkin's lymphoma. This cell is not present in the cancerous tissues of Non-Hodgkin's lymphoma and therefore, is the basis of their segregation into two classes.

Hodgkin's Lymphoma

It is a type of cancer that occurs primarily in the lymph nodes. Based on the appearance of the cancerous tissues in a biopsy, it is grouped into two types, nodular lymphocyte predominant Hodgkin's lymphoma (NLPHL) and Classical Hodgkin's lymphoma.

Symptoms
Like most cancers, a person suffering from Hodgkin's lymphoma may or may not manifest all its symptoms. Some patients remain asymptomatic till the disease has reached an advanced stage. Some of the symptoms are:

• Painless, rubbery, enlarged lymph nodes
• Unexplained exhaustion and fever
• Dry cough and breathing problems
• Severe itching in the legs or in the entire body
• Profuse night-time sweating
• Weight loss

Treatment
The treatment depends upon the stage of the disease, and involves chemotherapy and radiation therapy. Although many factors determine which treatment option is to be used, generally stage I and stage II are treated with radiation therapy. Patients with 'B' symptoms, those with advanced stage II, stage III and stage IV, are treated with chemotherapy.

Non-Hodgkin's Lymphoma (NHL)

Non-Hodgkin's lymphoma is a cancer of the lymphoid system. It is divided into three types: high-grade, intermediate-grade and low-grade. High-grade NHL progresses fast and can be life-threatening if left untreated. However, if detected, it is curable. Low-grade NHL, on the other hand, is slow-growing and does not produce symptoms easily. But it is not curable by the methods used for treating cancers.

Symptoms
Many of the symptoms of Non-Hodgkin's lymphoma are similar to those of Hodgkin's lymphoma, like fatigue, weight loss, fever, itching and night sweats. Swollen and painless lymph nodes develop in the neck region, armpits and inguinal region. Persistent coughing may indicate cancer in the thymus. If the cancer spreads to the brain, symptoms like headache, cognitive problems and seizures may be seen. Many NHL patients have abdominal swelling and pain.

Treatment
It is based on whether the cancer is high-grade, intermediate-grade or low-grade and several other factors. The treatment options include radiation therapy, chemotherapy, monoclonal antibody therapy and autologous stem cell transplantation.

Lymphangitis

Lymphangitis is an inflammation of the lymphatics (lymph channels) due to an infection by a microbe or some chemical irritant. It occurs when an infection or inflammation occurs somewhere else and the microbe or the irritant is transported along with lymph fluid through the lymphatics. This leads to a secondary infection and inflammation, distinct from the infection or inflammation at the primary site. The infection affects the lymph vessel walls, which become inflamed. The consistency of the lymph changes and becomes thick. Microbes that cause lymphangitis mostly enter the lymphatics via a skin infection.

Causes
Bacteria such as Streptococci, Staphylococci and even Neisseria can cause lymphangitis. Nodular lymphangitis, which is another form of this disease in which nodules form below the skin, is caused by microbes like Mycobacteria, Nocardia and Sporothrix, Leishmania, Francisella, etc. Additionally, cancer cells can colonize the lymph vessels and block them.

Symptoms
Red streaks or lines are visible on the skin, charting the course of the inflammation, which runs along the inflamed lymphatic vessels to the closest lymph node. This is accompanied with fever, pain, swelling and tenderness.

Treatment
The primary infection due to which lymphangitis has occurred is treated, usually with antibiotics. If not treated, the infection may spread to the blood stream, causing septicaemia, which is a life-threatening condition. If lymphatic fluid is trapped, it may be drained by an incision. A bandage is applied if the lymphangitis has affected an extremity.

Splenomegaly

Splenomegaly is a condition in which the spleen becomes enlarged, tender and painful. It can occur due to a number of reasons, ranging from certain infections to cancers. Many people remain asymptomatic while others have symptoms like tiredness, feeling satiated even after eating a small amount of food, and increased susceptibility to infections.

Causes
Bacterial, viral and parasitic infections, pathological conditions of the liver, haematological diseases, autoimmune disorders and several kinds of cancers can cause splenomegaly.

Treatment
In theory, treatment of the underlying conditions causing the enlarged spleen will treat the splenomegaly as well. If this is not possible, radiation therapy or surgical removal of the spleen are the options available to those suffering from the condition.