Introduction:
Hemolytic uremic syndrome (HUS) is characterized by hemolytic anemia, thrombocytopenia and acute renal failure. HUS is the most common cause of acute renal failure among children. HUS can be divided into typical and atypical. Typical HUS, D (+) is preceded by diarrhea, while atypical is not, and for this reason it is called D (-). The third possible type of HUS is secondary HUS.

The objective:
The objective of the study was the presentation of the case of a 7-year old patient suffering from recurrent, atypical HUS. On admission, laboratory tests revealed massive anemia, thrombocytopenia and acute renal failure. The boy required haemodialysis and plasmapheresis with fresh frozen plasma. Treatment resulted in patient’s state improvement, lab tests presented no abnormalities. After two weeks the relapse took place. Immunological tests which were established earlier, revealed the presence of anti-factor H antibodies. The patient required the same treatment: haemodialysis and plasmapheresis. Apart from this, intravenous IgG (IVIg) infusions and immunosuppressive (mycophenolate mofetil, MMF) treatment were applied. Patient’s state improved, anti-factor H antibodies titer decreased, kidney function is normal, MMF therapy is continued.

Conclusions:
Knowledge of the type of the process underlying atypical HUS etiology allows the implementation of a proper treatment, which significantly affects future prognosis. Key words: atypical hemolytic-uremic syndrome, acute renal failure, complement, factor H, children