Hyperhemolysis syndrome is an atypical form of transfusion reaction, it has been described with a frequency of 4% in patients with sickle cell anemia after transfusion of apparently compatible red blood cells. It is a rare and serious condition characterized by a drop in hemoglobin after transfusion, reaching a value lower than the pre-transfusion value. Hemolysis occurs not only of transfused red blood cells, but also of autologous red blood cells. Not only anti-erythrocyte antibodies, but also anti-HLA antibodies or those directed against heterologous proteins, are expected to activate the complement that leads to hemolysis.

A 25-years-old woman with a history of sickle cell disease and previous transfusions due to pain crises. The patient was admitted for acute chest syndrome and lowering of the sensorium with the need for non-invasive ventilatory support (Hb 6.8 g/dL) for which she received 5 units of packed RBCs and 3 sessions of partial exchange transfusions were performed with the patient's compatible phenotype, but the first RBCs was with partial phenotype Jk(a+b+). On admission, the patient's erythrocyte antigen phenotype was C+, c+, E-, e+, K-, Jk(a+b-), Fy(a-b+), M-, S-, s+, and her antibody history included anti-M and anti-Fya had been detected 8 and 5 years prior, respectively. At the time of partial exchange transfusions, her Direct Antiglobulin Test (DAT) was negative and RBC units that lacked E, K, Fya and M were transfused and posttransfusion Hb was 7.9 g/dL. On day 10 she developed a fever of 38°C, and on day 11 her Hb decreased to 1.9 g/dL, LDH level was 5398 U/L and her reticulocyte count was 279000 uL. The patient evolved with hypoxemia, dark urine and hemodynamic instability, for which she was admitted to the intensive care unit. The DAT indicated the presence of IgG, IgM and C3d on the patient's RBCs and her antibody screen showed anti-M, anti-Fya, and anti-Jkb and undetermined antibody. These results pointed to a new alloantibody anti-Jkb and the patient was diagnosed with a delayed hemolytic transfusion reaction with hyperhemolysis syndrome secondary to anti-Jkb. Her hospital course was complicated by worsening hypoxemia and acute tubular necrosis for which a transfusion of less incompatible red blood cells was performed in 20 mL aliquots in 20 minutes. She was successfully treated with IGIV, high-dose prednisone, erythropoietin, vasopressor and fluids.

Hyperhemolysis syndrome is defined as a significant drop in hemoglobin within 21 days posttransfusion associated with new red cell alloantibody, reticulocytosis and significant LDH. One of the proposed mechanisms for autologous hemolysis is based on the development, or increase, of circulating autoantibodies, resulting from previous transfusional stimuli. In this case, the detection of anti-Jkb was challenging as the patient had low titers in the screening tests and after mismatched transfusion, titers started to rise and produce the hyperhemolysis syndrome. The treatment consists of suspending the transfusion, corticosteroid therapy and/or administration of IGIV, avoiding new transfusions.

This case report highlights the need to recognize this hyperhemolysis syndrome and, consequently, provide adequate therapy, leading to a decrease in the risk of death. A shared decision-making process between the hematologist and the transfusion medicine specialist is critical.