Bone marrow failure in a dog

A 7‐month old Boxer bitch with lethargy and inappetence of several days' duration was found to have pancytopenia. A bone marrow aspirate contained many lymphocytes and immature myeloid cells but few erythrocyte precursors; marrow phagocytes appeared active and megakaryocytes were immature. Circumstantial evidence suggested that the cause of marrow failure was prior administration of thiacetarsamide, an organic arsenical. Recovery was spontaneous and within four weeks the haemo‐gram was normal, except that platelet numbers were not fully restored. The bitch was examined 6 months later because of a recurrence of signs, with several syncopic episodes during the preceding week. A severe non‐regenerative anaemia was present, with absence of erythroid precursors from bone marrow. Neutrophil and platelet counts were normal. The cause of the erythrocyte aplasia was not determined. The dog was given blood transfusions, oxymetholone and prednisolone but died after one month. A post‐mortem marrow sample contained many erythroid cells, some with morphological abnormalities suggesting dyserythropoiesis.