First Case Report of Precursor-Targeted Immune-Mediated Anaemia in a Dog From Italy Lacking Rubriphagocytosis and With Severe Hyperferraemia: Diagnosis, Treatment, and Clinical Outcome.

Abstract

Precursor-targeted immune-mediated anaemia (PIMA) is an uncommon and poorly understood cause of persistent non-regenerative anaemia in dogs and cats, characterised by ineffective erythropoiesis and frequently associated with rubriphagocytosis (RP) in bone marrow samples. An immune-mediated mechanism directed against erythroid precursors is suspected, although the exact pathogenesis remains unclear. Most affected animals respond to glucocorticoids, while additional immunosuppressants are required in refractory cases. An 8-year-old spayed mixed-breed female dog was referred to the Veterinary Teaching Hospital (Valenzano, Italy) with a 70-day history of progressive non-regenerative anaemia. Initial complete blood count revealed moderate, normocytic, normochromic anaemia, while serum biochemistry showed mild increases in alanine aminotransferase, total serum iron, and C-reactive protein without signs of haemolysis. Bone marrow cytology demonstrated erythroid hypoplasia with maturation arrest but no RP. Flow cytometric testing confirmed anti-RBC antibodies, supporting a diagnosis of PIMA. The dog was treated with prednisolone (2 mg/kg/day), which induced a rapid regenerative response within 3 days. Due to steroid-related adverse effects, mycophenolate mofetil was introduced, allowing gradual tapering and eventual discontinuation of corticosteroids. Hyperferraemia resolved after immunosuppressive therapy. After one year, the dog remains clinically stable on mycophenolate monotherapy with sustained haematologic remission. This case highlights the diagnostic challenges of PIMA, particularly in the absence of RP, and emphasises the importance of including this rare condition in the differential diagnosis of dogs with persistent non-regenerative anaemia, even when clinical and cytological features are atypical.