Complement deficiencies are disorders that occur when the body has low or nonexistent levels of specific proteins needed for proper immune function. Healthy immune function is important to protect the body from disease and infections. These proteins, which are part of the complement system, help destroy harmful invaders, such as bacteria and viruses, that enter the body.
The complement system is a group of more than 20 different proteins involved in the immune response. The complement proteins can destroy invading substances in many ways. For instance, the proteins can kill bacteria directly by poking holes in them. The proteins can also kill foreign substances that are attached to other proteins called antibodies. In addition, the complement proteins can bind to foreign substances, which triggers white blood cells to engulf and destroy the invaders.
Symptoms of complement deficiencies vary depending on the specific protein involved and severity of the deficiency. Patients with complement deficiencies are often vulnerable to frequent infections, especially pneumonia or meningitis (infection that causes inflammation of the membrane that surrounds the brain and spinal cord). Also, an estimated 90% of patients with complement deficiencies also develop autoimmune disorders, such as lupus. Autoimmune disorders occur when the immune system launches an attack against body cells because they are mistaken for harmful invaders.
Some patients are born with complement deficiencies. Researchers estimate that three out of 10,000 people inherit the disorder worldwide. Others may develop complement deficiencies as a result of other medical conditions, such as liver disease.
There is currently no cure for inherited complement deficiencies. Instead, patients receive medications called antimicrobials for infections and/or drugs called immunosuppressants for autoimmune disorders. If the complement deficiency develops as a result of another medical condition, such as liver disease, the disorder will be cured once the underlying cause is treated.
The average life expectancy for patients with complement deficiencies varies considerably. Some patients may experience no signs of the disease and live normal, healthy lives. Others may experience severe infections that can lead to death. Autoimmune disorders may lead to organ failure if they are not properly managed with immunosuppressant drugs.
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