Pure red cell aplasia due to Parvovirus B19 infection and atezolizumab: case report and literature review.

The benefits of immune checkpoint inhibitor (ICI)-based treatment are tempered by immune-related adverse events (irAEs). However, various aspects of the pathogenesis of these events remain unclear. Here, we report the case of a 69-year-old patient with advanced hepatocellular carcinoma (HCC) developing severe anemia after 15 cycles of atezolizumab/bevacizumab. The initial workup based on bone marrow aspirate demonstrated selective deficiency of the erythroid line, CD8+ T-cell infiltrate, and Parvovirus B19 PCR (PVB19) positivity, suggesting a pure-red cell aplasia (PRCA) secondary to PVB19 infection. The patient received blood transfusion, intravenous immunoglobulin, and temporary atezolizumab/bevacizumab treatment interruption. After discharge, due to good clinical condition and stable Hb values, atezolizumab/bevacizumab therapy was resumed; however, after three cycles of re-treatment, a recurrence of anemia necessitating blood transfusions every 10 days and hyporeticulocytaemia was observed. The bone marrow aspirate was reassessed, and pure ICI-related red blood cell aplasia was suspected. Prednisone treatment (1 mg/kg per day) was initiated, resulting in progressive improvement of hemoglobin levels without the need for blood transfusion. After resolution of the anemia, treatment with atezolizumab was resumed without recurrence of anemia. This case highlights the potential for atezolizumab to be associated with hematological adverse events, possibly in conjunction with a PVB19 infection.