Bothmanifestwiththrombocytopenia,microangiopathichemolyticanemia,andrenalfailure;feverandCNSinvolvementaremoretypicalofTTP.
TTP: CausedbyacquiredorinheriteddeficienciesofADAMTS13,aplasmametalloproteasethatcleavesvery-high-molecular-
Complications of Transfusion weightmultimersofvWF.DeficiencyofADAMTS13resultsinabnormallylargevWFmultimersthatactivateplatelets.
•Hemolytic uremic syndrome: Causedbydeficienciesofcomplementregulatoryproteinsoragentsthatdamageendothelialcells,suchasaShiga-liketoxinelaboratedbyE. coli strainO157:H7.Theendothelialinjuryinitiatesplateletactivation,plateletaggregation,andmicrovascularthrombosis.
AutosomaldominantdisordercausedbymutationsinvWF,alargeproteinthatpromotestheadhesionofplateletstosubendothelialcollagen.
Typicallycausesamildtomoderatebleedingdisorderresemblingthatassociatedwiththrombocytopenia.
Hemophilia A: X-linkeddisordercausedbymutationsinfactorVIII.AffectedmalestypicallypresentwithseverebleedingintosofttissuesandjointsandhaveaPTT.
Hemophilia B: X-linkeddisordercausedbymutationsincoagulationfactorIX.ItisclinicallyidenticaltohemophiliaA.
Blood products often are rightly called “the gift of life,” permitting people to survive traumatic injuries and procedures such as hematopoietic stem cell transplantation and complex surgical procedures that would otherwise prove fatal. Over 5 million red cell transfusions are given in
U.S. hospitals each year. Thanks to improved screening of donors, blood products (packed red blood cells, platelets, and fresh-frozen plasma) are safer than ever before.
Nevertheless, complications still occur. Most are minor and transient. The most common is referred to as a febrile nonhemolytic reaction, which takes the form of fever and chills, sometimes with mild dyspnea, within 6 hours of a transfusion of red cells or platelets. It is thought that these reactions are caused by inflammatory mediators derived from donor leukocytes. The frequency of these reactions increases with the storage age of the product and is decreased by measures that limit donor leukocyte contamination. Symptoms respond to anti-pyretics and are short-lived.
Other transfusion reactions are uncommon or rare, but can have severe and sometimes fatal consequences, and therefore merit brief discussion.
Severe, potentially fatal allergic reactions may occur when blood products containing certain antigens are given to previously sensitized recipients. These are most likely to occur in patients with IgA deficiency, which has a frequency of 1:300 to 1:500 people. The reaction is triggered by IgG antibodies that recognize IgA in the infused blood product. Fortunately, most patients with IgA deficiency do not develop such antibodies, and these severe reactions are rare, occurring in 1 in 20,000 to 1 in 50,000 transfusions. Urticarial allergic reactions may be triggered by the presence of an allergen in the donated blood product that is recognized by IgE antibodies in the recipient. These are more common, occurring in 1% to 3% of transfusions, but they are generally mild.