HOW PARTIAL C7 DEFICIENCY WITH CHRONIC AND RECURRENT BACTERIAL-INFECTIONS CAN MIMIC TOTAL C7 DEFICIENCY - TEMPORARY RESTORATION OF HOST C7 LEVELS FOLLOWING PLASMA TRANSFUSION

An apparently completely complement C7-deficient patient with refracto ry otitis media and two episodes of meningococcal disease was given th erapeutic plasma transfusions in 1992 and 1994. Following these transf usions unexpected changes were found in C7 levels. Immediately after t ransfusion the serum C7 levels failed to rise to the expected levels b ut then rose to 5-10% of the normal mean during the next 5 days and re mained at that level for more than 2 weeks before eventually returning to zero. The patient's DNA genotyped C7M, and therefore C7 N donor pl asma was selected for the second transfusion to allow identification o f the source of the C7 circulating post-transfusion. This C7 phenotype d C7 M, demonstrating it to be of recipient origin. Therefore, the app arently completely C7-deficient patient was able to secrete some C7. B y a combination of DNA typing and isoelectric focusing of the C7 appea ring after transfusion, it was demonstrated that the patient was heter ozygous for combined subtotal C6/C7 deficiency (inherited from his fat her) and a different, so far uncharacterized, subtotal C7 deficiency ( inherited from his mother). The low amount of C7 secreted appeared to be constantly consumed, probably by generation of C5b6 as a result of his chronic infection. He had been shown to have circulating C5b6 most of the time, and thus only when sufficient exogenous C7 was given to consume the free C5b6 did his own C7 appear in circulation.