Lymphoid hyperplasia is the swelling of lymph tissue due to an accelerated increase of lymphocytes when the immune system perceives a threat to the body. Lymphoid hyperplasia, or lymphoid hypertrophy, can occur in the presence of bacteria, a virus, or anomalous tissue growth. The increase in thenumber of lymphocytes, commonly associated with the body's immune response, can be initiated by a local or systemic infection. Physicians refer to lymphoid hyperplasia as benign, reactive, or a combination of the two.
Lymphocytes, or B cells, are white blood cells that originate in the bone marrow and travel through the blood and lymphatic systems. An immune response is triggered when the body senses an invasion and lymphocytes attempt to prevent the foreign invader from traveling throughout the circulatory system. Part of the immune system, also known as the reticuloendothelial system, consists of the lymph glands. As blood passes through the lymph system, it is constantly monitored by lymphocytes. Depending on the type of pathogen, the lymphocytes either develop antibodies against that substance or devour the threat in a process known as phagocytosis.
Lymphocyte populations in the locality, or throughout the system, begin increasing as part of the normal defense response. The new lymphocytes are generally not released to travel throughout the system until they have reached maturity. When proliferation occurs in a particular area, lymph glands begin swelling. Localized infections in the upper respiratory system, for example, commonly produce parotid gland swelling in the neck. The proliferation and swelling continue until the infection resolves naturally or is treated with medication.
Appendicitis is another example of localized lymphoid hyperplasia. The condition usually begins when a blockage occurs between the appendix and the part of the intestine known as the cecum. The blockage might be caused by trapped stool, excess mucus, or lymphatic swelling. Following the blockage, bacteria circulating normally through the intestine may invade the appendix wall, triggering the immune system. Swelling, inflammation and discomfort are signs that the immune system has initiated a response.
Castleman's disease is a rare disorder that usually produces benign growths in one location or throughout the body. These growths might appear in the neck, chest, stomach, or intestinal regions. Lymphoid hyperplasia generally occurs as lymphocytes attempt to combat the invasion of foreign tissue. Patients having this malady typically experience fever, weight loss, and skin rashes along with anemia caused by red blood cell destruction. A chemical response generally includes an increase in gamma globulin as well as liver and spleen enlargement from increased populations of lymphocytes.