In postinfectious glomerulonephritis, what is typically seen in complement levels?

In postinfectious glomerulonephritis, typically seen following infections such as streptococcal infection, complement levels are characteristically low. This occurs because the immune response to the infection leads to consumption of complement components, particularly C3. The formation of immune complexes and the subsequent activation of the complement cascade is a key feature in the pathophysiology of postinfectious glomerulonephritis.

As the disease progresses, the body's complement system becomes overwhelmed, resulting in decreased levels of certain complement proteins in the bloodstream. This reduction in C3 levels is indicative of the disease process and supports the diagnosis. Other complement levels, such as C4, are often less affected in this setting. Understanding this complement consumption is essential in distinguishing postinfectious glomerulonephritis from other types of glomerular diseases, such as those associated with systemic diseases like lupus, where complement levels may show different patterns.

In contrast, elevated, normal, or variable levels of complement would not align with the established understanding of postinfectious glomerulonephritis, where decreased C3 levels are a hallmark finding.