Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (832 page)

   Arthritis

   Nephritis

   Rashes

   Pneumococcal infections

   Heterozygous mutations in plasma factors H and I result in consumption of C3, predisposing patients to infections and glomerulonephritis.

   A genetic deficiency of complement regulatory proteins has been identified in 40–80% of cases of
atypical hemolytic uremic syndrome (aHUS)
, a rare syndrome of microangiopathic hemolysis, thrombocytopenia, and renal failure. A deficiency of factor H (the most frequent abnormality in aHUS), C3 mutations, and deficiencies of membrane cofactor protein, factor I, factor B, and thrombomodulin.

   Properdin (alternate pathway) deficiency is transmitted as an X-linked condition, and these males are affected by
Neisseria meningitidis
, often of unusual types.

   Lectin pathway deficiencies are rare: deficiencies of MBL, MBL-associated protease 2, and ficolin-3 are associated with pyogenic infections, especially with encapsulated bacteria.

Increased

In inflammatory conditions that increase acute-phase reactants.

   
Complement may be normal or increased in:

   Juvenile rheumatoid arthritis

   Palindromic arthritis

   Pseudogout and gout

   Reiter syndrome