A 6-year-old boy presented with pallor and jaundice in the setting of anemia (hemoglobin, 6.6 g/dL), reticulocytosis (23.3%; 0.420 × 10⁶ cells per μL), and hemolysis (lactate dehydrogenase 667 U/L, haptoglobin <10 mg/dL, total bilirubin 2.2 mg/dL). A direct antiglobulin test, initially 1+, became negative despite persistent hemolysis. A peripheral blood smear (panel A, Wright-Giemsa stain) with red blood cell (RBC) agglutinates and marked polychromasia supported a diagnosis of autoimmune hemolytic anemia (AIHA). His hemoglobin stabilized after 2 packed RBC (PRBC) transfusions (hemoglobin 9.7 g/dL), and he was discharged. He presented again with fever and new onset knee pain 8 days later. His examination was significant for the absence of lymphadenopathy or organomegaly. One day later, his laboratory test results showed pancytopenia with white blood cell count 3.9 × 10³ cells per μL and posttransfusion hemoglobin 6.4 g/dL. He had relative reticulocytopenia (5.81%; 0.105 × 10⁶ cells per μL) and thrombocytopenia 90 × 10³ cells per μL. A repeat peripheral blood smear (panel B, Wright-Giemsa stain) demonstrated an absence of significant polychromasia and Rouleaux formation of rare RBCs. Parvovirus serology (immunoglobulin G [IgG] and IgM) was negative; however, >1.38 × 10¹⁰ IU/mL of parvoviral DNA copies were detected by polymerase chain reaction, suggestive of the cause of bone marrow aplasia but not AIHA. A super Coombs test identified an IgG component to his antibody-mediated hemolysis. Remission occurred after 7 PRBC transfusions. In addition, he received a maximum dose of 4 mg/kg per day methylprednisolone divided into 1 dose every 6 hours, and 4 once-per-week doses of 375 mg/m² of rituximab.

This case highlights the key smear findings of AIHA, as well as the danger of aplastic crisis in those with active hemolysis.