Preferred Minimum: 8 mL whole blood Absolute Minimum: 4 mL whole blood

Complement Factor B Atypical Hemolytic-Uremic Syndrome The clinical manifestations of hemolytic-uremic syndrome (HUS) include hemolytic anemia, thrombocytopenia and acute renal failure. Most cases are associated with epidemics of diarrhea caused by verocytotoxin-producing bacteria. Atypical hemolytic uremic syndrome (aHUS) is a rarer disease. It is not associated with Stx-HUS infection and neither does it present with watery, bloody diarrhea (Warwicker et al., 1998). It can be either sporadic or familial, and has an extremely unfavorable prognosis, with about 50% of persons progressing to ESRD and 25% dying during the acute illness; transplantation in many survivors is unsuccessful (Schieppati et al., 1992; Taylor et al., 2004). Genetic studies have shown that approximately 50% of cases of aHUS are caused by mutations in MCP, CFH and IF (Caprioli et al., 2006). Gain of function mutations in Complement Factor B have been identified in persons with aHUS (Goicoechea de Jorge et a., 2007). Identifying the genetic cause of aHUS is extremely important as it can help to direct clinical treatment decisions. Complement Factor B (FB) Factor B is a zymogen that carries the catalytic site of the complement alternative pathway convertase C3bBb. The FB gene contains 18 exons and encodes the 764 amino acid protein, Complement Factor B. There have been at least two reported cases of Factor B-deficient patients. Sensitivity is greater than 99%.