Congenital dyserythropoiesis and polymyopathy without cardiac disease in male Labrador retriever littermates

Abstract

Background: Two Labrador retriever littermates were identified based on incidentally noted marked microcytosis and inappropriate metarubricytosis. Muscle atrophy was noted and associated with distinctive pathological findings in biopsy samples from 1 dog studied. The disorder represents a rare clinical entity of suspected congenital dyserythropoiesis and polymyopathy. Clinicopathologic changes were similar to a previously reported syndrome of congenital dyserythropoiesis, congenital polymyopathy, and cardiac disease in 3 related English Springer Spaniel (ESS) dogs, but the dogs reported here did not have apparent cardiac disease.

Interventions: Bone marrow aspiration, electromyography, muscle biopsies, and an echocardiogram were performed on dog 1. Results supported dyserythropoiesis and congenital polymyopathy similar to reports in ESS dogs, but did not identify obvious cardiac disease.

Conclusion: The clinicopathologic changes of dyserythropoiesis and polymyopathy provide an easily recognizable phenotype for what appears to be a low morbidity syndrome. Early recognition may decrease unnecessary testing or euthanasia.

Keywords: anemia; dyserythropoiesis; metarubricytosis; microcytosis; muscle atrophy; polymyopathy; regurgitation.

FIGURE 1

Representative blood film image of case 1 displaying a single metarubricyte as well as moderate to marked overall poikilocytosis characterized by schistocytes, codocytes, and acanthocytes. Wright‐Giemsa, ×100 objective

FIGURE 2

Representative cytologic bone marrow images of case 1 illustrating dysplastic changes and erythrophagocytosis. Wright‐Giemsa, ×100 objective. A, Atypical mitotic figure; B, cytoplasmic vacuolation of metarubricytes. Note the contrast of vacuolation (left metarubricyte) compared to water artifact (adjacent right metarubricyte), C, binucleated erythroid precursor; D, nuclear blebbing within a metarubricyte; E, cytoplasmic bridging of rubricytes; F, macrophage displaying metarubricyte phagocytosis

FIGURE 3

Cryosections from the triceps muscle of case 1 stained with hematoxylin and eosin (H&E), A, and modified Gomori trichrome, B, or reacted for cytochrome C oxidase, C, and succinic dehydrogenase, D, activities. Prominent findings are variability in myofiber size, central nuclei (arrow heads), and central accumulations of reactivity that are basophilic with the H&E stain and red with the modified Gomori trichrome stain, and dark brown or dark blue with the cytochrome C oxidase and SDH reactions, respectively (arrows)