Pure red cell aplasia (PRCA) is a rare hematologic disorder characterized by reticulocytopenic, normocytic anemia with absence of red cell precursors in bone marrow, normal granulopoiesis, and megakaryopoiesis. The disease may be associated with viral infections, large granular lymphocytic leukemia, chronic lymphocytic leukemia, or thymoma, but the most common form is idiopathic. Refractory PRCA may respond to more profound immunosuppression with anti-CD52.

To describe a refractory PRCA patient treated with anti-CD52 humanized monoclonal antibody, alemtuzumab, with good response.

A 52-year-old male patient with hemophilia A, previously treated with cryoprecipitate and currently using prophylactic Factor VIII, presents to healthcare with severe asthenia, no bleeding episodes during the period. Laboratory evaluation: Hb 3.4 g/dL; Ht 10.6% VCM 95; WBC 6.490 × 109 /L; Platelets 196 × 109 /L, intense reticulocytopenia (25 × 109 /L). He had normal renal function, liver function, LDH, vitamin B12, folic acid, iron profile; serology with positive anti-HCV. Bone marrow evaluation showed 50-60% cellularity with intense hypoplasia of the erythroid series, granulocytic series with no changes in morphology or maturation pattern, and normal megakaryocytes with no signs of dysplasia. After investigation with immunoglobulin dosing, chest CT, flow cytometry for LGL, and serology for parvovirus, all normal, the diagnosis of constitutional APSV was confirmed. Treatment with cyclosporine (CSA) at a dose of 6mg/kg was initiated, with no reticulocyte response. In addition, he evolved with progressively increasing bilirubin levels (BT 7.4 BD 5.6) concomitant with a significant increase in Hepatitis C viral load (380,667 IU/mL Log: 5.58). Immunosuppression was discontinued, treatment with sofosbuvir and simeprevir was initiated, with good viral response. However, he required red blood cell transfusions every 2-3 weeks; new therapy was restarted with CSA and prednisone. The patient did not tolerate this treatment and developed severe thrombocytopenia and no improvement in hemoglobin levels. Considering the high risk of bleeding, CSA was discontinued. Platelet count normalized but he continued to require mensal RBC transfusion. At this point, second-line therapy with IV Alentuzumab, 3 mg dose followed by 6 weekly 15 mg doses (total 96 mg), coupled with infectious prophylaxis, has been proposed. Response occurred as early as the third infusion, as documented by a rapid increase in reticulocyte count. Within seven weeks the patient had a complete response (Hb 12.4 g/dL, Vg 35.3% and reticulocytes 170 × 109/L). He had no toxicity-related intercurrences and remained with a complete response after six months of treatment. Unfortunately, a further progressive drop in hemoglobin after nine months from the end of the first treatment was observed. We opted to restart Alentuzumab at a dose of 15 mg/month, and follow with this maintenance dose. After the third application, the patient again showed a complete response (Hb 14.3 g/dL and VG 40.5%). Currently, the patient continues to use the medication every 45 days with a maintained hemoglobin level.

Small case series cite Alentuzumab for refractory APSV as a treatment possibility with 63% overall response. We suggest use in refractory cases, followed by maintenance dosing to avoid relapse in long-term follow-up.