Atypical hemolytic uremic syndrome: update on the complement system and what is new.
Atypical hemolytic uremic syndrome (aHUS) is a rare disease of microangiopathic hemolytic anemia, thrombocytopenia, and predominant renal impairment. It is characterized by the absence of Shiga toxin-producing bacteria as a triggering factor. During the last decade, aHUS has been demonstrated to be a disorder of the complement alternative pathway dysregulation, as there is a growing list of mutations and polymorphisms in the genes encoding the complement regulatory proteins that alone or in combination may lead to aHUS. Approximately 60% of aHUS patients have so-called 'loss-of-function' mutations in the genes encoding the complement regulatory proteins, which normally protect host cells from complement activation: complement factor H (CFH), factor I (CFI) and membrane cofactor protein (MCP or CD46), or have 'gain-of-function' mutations in the genes encoding the complement factor B or C3. In addition, approximately 10% of aHUS patients have a functional CFH deficiency due to anti-CFH antibodies. Recent advances in understanding the pathogenesis of aHUS have led to a revised classification of the syndrome. Normal plasma levels of CFH and CFI do not preclude the presence of a mutation in these genes. Further, genotype-phenotype correlations of aHUS have clinical significance in predicting renal recovery and transplant outcome. Therefore, it is important to make a comprehensive analysis and perform genetic screening of the complement system in patients with aHUS to allow a more precise approach, especially before transplantation. This may also provide opportunities for more specific treatments in the near future, as complement inhibition could represent a therapeutic target in these patients who have a considerably poor prognosis in terms of both mortality and progression to end-stage renal disease and a great risk of disease recurrence after transplantation.
Hirt-Minkowski
Patricia
P
Division of Transplantation Immunology and Nephrology, University Hospital Basel, Basel, Switzerland. phirt@uhbs.ch
Dickenmann
Michael
M
Schifferli
Jürg A
JA
D000818:Animals; D003167:Complement Activation / Q000276:immunology*; D003165:Complement System Proteins / Q000378:metabolism / Q000502:physiology*; D006463:Hemolytic-Uremic Syndrome / Q000175:diagnosis / Q000276:immunology* / Q000378:metabolism* / Q000628:therapy; D006801:Humans; D009154:Mutation / Q000235:genetics; D010951:Plasma Exchange / Q000639:trends; D033581:Stem Cell Transplantation / Q000639:trends
D003165:Complement System Proteins