BACKGROUND: Hemolytic uremic syndrome consists of a triad of acquired hemolytic 
anemia, thrombocytopenia and renal failure.
AIM: Our objectives were to determine epidemiology, clinical and laboratory 
characteristics of patients with atypical hemolytic uremic syndrome (aHUS) to 
determine the relationship between the complement protein deficit and aHUS in 
the Tunisian population.
METHODS: We studied retrospectively four cases of atypical HUS in adults 
admitted in the Nephrology Department of Fattouma Bourguiba Universitary 
Hospital in Monastir between 2000 and 2008.
RESULTS: Three patients had renal failure that required dialysis. One of them 
received kidney transplantation with no further recurrence of aHUS. Three 
patients had normal C3, C4, CFH, and FB levels, and in all patients anti-FH 
autoantibodies were absent. The kidney biopsy of one patient showed in addition 
to lupus glomerulonephritis histological findings consistent with TMA. A 
decrease in C3, C4 and CFH levels in this patient was found both before and 
after the cure.
CONCLUSION: Nephrologists should be aware of autoimmune conditions and genetic 
abnormalities of the complement regulatory genes as possible pathogenic 
mechanisms in atypical HUS patients.