Case Presentation: A 69-year-old male with hypertension, prostate cancer in remission, and recent diagnosis of lymphoma presented after experiencing a fall. Prior workup for abdominal pain, fever, night sweats, and weight loss revealed splenomegaly, anemia, and diffuse lymphadenopathy. Bone marrow biopsy demonstrated malignant lymphoma with prominent follicular helper T-cell component occupying 25-30% of the sampled bone marrow. Excisional lymph node biopsy confirmed: angioimmunoblastic T-cell lymphoma (AITL); he had yet to initiate treatment. On admission, patient was noted to have fever and pancytopenia. Empiric broad spectrum antibiotics were started for neutropenic fever. Investigations into infectious etiologies, including imaging, blood and urine cultures, and a respiratory viral panel, were unrevealing. His presentation was ultimately attributed to lymphoma progression, and antibiotics were discontinued. Oncology initiated induction chemotherapy. Following this, his pancytopenia persisted with patient now dependent on transfusions. He received antimicrobial neutropenic prophylaxis, daily filgrastim, and allopurinol for tumor lysis. Transfusions were ordered for hemoglobin < 7 g/dL and platelets < 10,000. These requests were delayed by the blood bank for serologic problems in preparing red cell components for transfusion. Patient had positive warm autoantibody and direct antiglobulin test (DAT). Coagulation profile was normal except for elevated D-dimer. Additional serologic testing revealed normal B12, folate, and G6PD levels, mildly elevated LDH and ferritin, and EBV/CMV studies consistent with past exposure. Peripheral smear showed rare schistocytes. Analysis of his serum by blood blank revealed Anti-Kpb antigen. Presence of this antibody underscored the several-day delays in transfusions due to challenges in procuring Kpb-antigen-negative blood. While awaiting blood products, patient’s hemoglobin remained stably low without life-threatening drops or significant bleeds.
Discussion: This case of AITL highlights an example where the selection of compatible blood for transfusion was extremely difficult. This patient had a positive DAT, which can be nonspecific and does not necessarily signal an autoimmune hemolytic anemia. In this case, patient was found to have a rare autoantibody resulting in a positive DAT in the absence of hemolysis. Few reports of autoantibodies with specificity directed towards Kpb antigen have been described. Anti-Kpb is an IgG antibody directed against the Kpb antigen in the Kell blood group system. Antigens of the Kell blood group are the third most potent at triggering an immune reaction, after the ABO and Rh blood groups. The Kpb antigen has a very high incidence and is found in nearly 100% of the population. Anti-Kpb has been implicated in severe hemolytic transfusion reactions and hemolytic disease of the fetus and newborn. Patients with anti-Kpb must receive Kpb-antigen-negative, Kp(b-), blood. Kp(b-) blood products are not readily available and often require days to obtain, owing to a nationwide search. Although the Kpb antigen is one of the most clinically significant Kell antigens, the anti-Kpb is an extremely rare antibody.
Conclusions: Clinicians should be suspicious of antibodies of the blood group systems when significant delays are encountered in procuring blood products. If antibodies are detected by the blood bank, clinicians must be prepared to navigate challenging management of patients who may require frequent transfusions.