Hypocomplementemia

Hypocomplementemia refers to a condition characterized by abnormally low levels of complement proteins in the blood. The complement system is a crucial part of the innate immune system, a network of proteins that helps defend the body against infections. These proteins work by identifying and destroying pathogens, marking them for removal by other immune cells, and triggering inflammation.

There are two main categories of hypocomplementemia: acquired and inherited. Acquired hypocomplementemia is far more common and can arise from various conditions. These include autoimmune diseases like systemic lupus erythematosus (SLE), where the body mistakenly attacks its own tissues, leading to excessive activation and consumption of complement proteins. Certain infections, particularly bacterial and viral ones, can also deplete complement levels. Some medications, such as those used to treat autoimmune disorders, can also suppress complement production or accelerate its clearance. Finally, certain types of glomerulonephritis, a kidney inflammation, are strongly associated with hypocomplementemia.

Inherited hypocomplementemia, though rarer, results from genetic defects affecting the production or function of specific complement proteins. These individuals are often predisposed to recurrent bacterial infections, particularly those caused by encapsulated bacteria.

Symptoms of hypocomplementemia can vary depending on the underlying cause and the severity of the complement deficiency. In acquired forms, symptoms are often related to the primary condition, such as joint pain, rash, and fever in SLE. Recurrent infections are a common manifestation, especially in inherited deficiencies. Diagnosis is typically made through blood tests that measure the levels of various complement components. Management focuses on treating the underlying cause and preventing or managing infections.