Use of Human Intravenous Immunoglobulin Therapy in Two Dogs with Non-Neoplastic Bone Marrow Disorders Refractory to Immunosuppressive Therapy

Immune-mediated non-neoplastic bone marrow disorders (NNBMD), including precursor-targeted immune-mediated anemia (PIMA) and myelodysplastic syndrome (MDS), can cause non-regenerative anemia in dogs and often fail to respond to immunosuppressive treatment. Human intravenous immunoglobulin (hIVIG) has been proposed as an immunomodulatory therapy for refractory hematologic disease in humans, but evidence in veterinary patients remains limited. This case report describes the adjunctive use of hIVIG and the associated clinical responses observed in two dogs with refractory NNBMD. A 10-year-old (3.2 kg) spayed female Maltese (case 1) showed persistent non-regenerative anemia, with hematocrit (HCT) 15.6-20.2% and reticulocyte production index (RPI) 0.12-0.69, requiring four transfusions over 10 months, and was diagnosed with PIMA based on bone marrow cytology demonstrating destruction of erythroid precursors. A 7-year-old (9.3 kg) intact female Dachshund (case 2) had sustained non-regenerative anemia (HCT 10.8-20.9%, RPI 0.12-0.40) necessitating eight transfusions over 20 months and was diagnosed with MDS characterized by dyserythropoiesis. Human intravenous immunoglobulin (0.5 g/kg over 6 h) was administered six times in case 1 and seven times in case 2 over a four-month period. After initiating hIVIG therapy, RPI increased (0→1.80 and 0.25→2.10 in cases 1 and 2), and HCT remained above 20% without further transfusions. To our knowledge, this is the first clinical report demonstrating the adjunctive use of hIVIG and associated hematologic improvement in canine NNBMD.