Abstract
Hemolytic uremic syndrome (HUS) is characterized by hemolytic anemia, thrombocytopenia and renal dysfunction. Approximately 10% of all cases are classified as atypical HUS because they are not caused by either verotoxin or streptococci. More than half of the patients with atypical HUS have complement abnormalities. DEAP-HUS (deficiency of CFHR proteins and CFH autoantibody positive) is characterized by an acquired factor which is an autoantibody against the complement factor H, and a genetic factor which is a homozygous deletion of CFHR1 and CFHR3 genes. A 4-year-old boy developed vomiting and diarrhea. Laboratory examinations at a local physician’s office revealed anemia, thrombocytopenia and renal dysfunction. After referral, he was found to have a low complement level (C3 50 mg/dl). No verotoxin was detected in his stool. We diagnosed him as having atypical HUS and started the administration of fresh frozen plasma. He received 3 plasma infusions and 5 plasma exchanges, and his anemia, thrombocytopenia and renal dysfunction resolved in 30 days. The patient is now 6 years old, and has not experienced any recurrence of HUS. We detected CFH autoantibodies in his serum by an ELISA method. We then investigated the expression of CFHR proteins by a Western blot analysis, which detected CFHR3 but not CFHR1. Furthermore, the copy number variation of CFH, CFHR3 and CFHR1 genes as detected by a MLPA method revealed the homozygous deletion of the CFHR1 gene. The diagnosis of DEAP-HUS was made.
