D70-D77: Other diseases of blood and blood-forming organs

D76: Other specified diseases with participation of lymphoreticular and reticulohistiocytic tissue

The diseases classified under D76 are a group of conditions that involve an abnormal response of the body's immune system, specifically within the lymphoreticular and reticulohistiocytic tissues. These tissues are crucial parts of the body's immune system, playing key roles in fighting off infections and other diseases. When these tissues are involved, the body may produce an excessive number of certain immune cells or these cells may act abnormally. The diseases can be triggered by various factors, including viruses, autoimmune diseases, or in some cases, the cause is unknown. Common symptoms are generally related to an overactive immune response and can include persistent fever, weight loss, fatigue, as well as swelling of lymph nodes. Over time, these conditions can lead to complications in various body systems, as the abnormal immune response can eventually result in significant tissue damage.