Diagnostic significance of hypocomplementemia

Abstract

Hypocomplementemia is an important marker for the presence of IC-mediated disease and can be used to assess disease activity. However, in interpreting the clinical significance of hypocomplementemia, the following must be kept in mind: 1) There are numerous non-immunologic conditions that also can cause hypocomplementemia. Furthermore, some of these conditions can cause a multisystem disease that, along with the hypocomplementemia, can closely resemble an IC-mediated systemic vasculitis. Furthermore, these nonimmunologic conditions that lower serum complement levels can complicate the course of patients with inactive IC-mediated disease, spuriously indicating that the disease is active. The most relevant of these differential diagnostic problems are listed in Table 2. 2) There are a few conditions (for example, pregnancy) that can raise serum complement levels, thereby possibly obscuring the presence of a disorder (such as, active SLE) that is lowering complement levels. 3) There are some conditions that might be expected to lower serum complement levels, because of their effect on protein metabolism, but do not. Nephrotic syndrome, and moderately poor nutrition are examples. All of these factors should be considered when interpreting results of serum complement levels in a given patient.

Synovitis in a Patient with IgG4-related Disease

“…Hypocomplementemia is generally divided into two types (16): immune-mediated, such as that seen in patients with systemic lupus erythematosus (SLE), rheumatoid vasculitis, systemic vasculitic syndromes and cryoglobulinemic vasculitis, and non-immunologic, including that due to malnutrition, liver cirrhosis and severe infection (16). Recently, it has been reported that hypocomplementemia is sometimes observed in cases of IgG4-RD (17).…”

Fibrillary Glomerulonephritis with Hepatitis C Viral Infection and Hypocomplementemia

“…Hypocomplementemia in FGN is rarely reported, as complement levels are typically normal in FGN as compared to other types of glomerulonephritis. [15] However, hypocomplementemia in patients with chronic HCV infection is common. [16,17] The literature on the treatment of FGN suggests that optimal treatment regimens typically used for other forms of glomerulonephritis (including the use of corticosteroids and/or cytotoxic agents, such as cyclophosphamide or cyclosporine) are ineffective with FGN, and half of all patients will rapidly progress to end-stage renal disease within 2-4 years.…”

All Things Complement

“…Conditions in which hepatic production of C proteins is altered can confound the interpretation of low C levels. Production of the C proteins increases in pregnancy, for example, whereas it decreases in patients with cirrhosis (28). Furthermore, the levels remain normal in many C-mediated diseases.…”

“…C Protein Levels. Decreased levels of plasma C3 and C4 have long been associated with active inflammation in patients with autoimmune and systemic inflammatory diseases (28). The levels of these proteins are determined by their rate of synthesis (primarily in the liver, but also by renal cells) and the rate of consumption.…”

“…The levels of these proteins are determined by their rate of synthesis (primarily in the liver, but also by renal cells) and the rate of consumption. They are sensitive indicators of activity in some diseases, such as diffuse proliferative lupus nephritis (28). Conditions in which hepatic production of C proteins is altered can confound the interpretation of low C levels.…”