BACKGROUND: Human epidermal growth factor receptor 2 (HER2)-positive breast cancer is commonly treated with docetaxel/carboplatin/trastuzumab (TCbH). While anemia is a common complication, progression to pure red cell aplasia (PRCA) is extremely rare. This report presents the case of a 45-year-old woman with right breast ductal carcinoma (cT3N2M0, HER2-positive) who developed PRCA following neoadjuvant TCbH and was effectively treated with cyclosporine.

CASE REPORT: A 45-year-old woman with right breast invasive ductal carcinoma (cT3N2M0, HER2-positive) received neoadjuvant TCbH. After the sixth cycle, she developed progressive anemia refractory to erythropoietin, with hemoglobin (Hb) decreasing to 34.2 g/L. After transfusion, she underwent modified radical mastectomy with pathological complete response. Postoperatively, anemia worsened with marked reticulocytopenia (reticulocytes 3.8×10⁹/L; 0.2%). Bone marrow examination revealed markedly reduced erythroid precursors. Acquired PRCA was diagnosed after excluding iron deficiency, megaloblastic anemia, hemolytic anemia, hematologic malignancies, autoimmune disorders, aplastic anemia, thymoma, and infections. Oral cyclosporine (100 mg twice daily) induced complete hematologic remission at 7 weeks and was tapered over 2 years. During the adjuvant trastuzumab/pertuzumab (HP) treatment, Hb remained ≥110 g/L. A heterozygous germline BRCA1 mutation (c.788delG) was identified. At the 4.5-year follow-up, there is no recurrence of either breast cancer or anemia.

CONCLUSIONS: This case highlights PRCA as a severe complication of TCbH therapy. Reticulocytopenia with refractory anemia warrants timely bone marrow examination. In this patient, cyclosporine was effective; after anemia correction, HP was tolerated. The observed gBRCA1 mutation is a hypothesis-generating finding requiring further validation.

Keywords: BRCA1 Protein, Breast Neoplasms, Case Reports, Cyclosporine, Pure Red-Cell Aplasia