Myelodysplastic syndrome in two dogs

Area of Science:

• Veterinary Medicine
• Hematology
• Canine Pathology

Background:

• Myelodysplastic syndrome (MDS) is a group of clonal hematopoietic stem cell disorders characterized by ineffective hematopoiesis and a high risk of transformation to acute myeloid leukemia.
• While MDS is recognized in humans, its presentation and progression in canine patients require further characterization.

Observation:

• This report details two canine cases exhibiting classic MDS indicators, including hepatomegaly, cytopenias, macrocytosis, and bone marrow dysplasia across all hematopoietic lineages.
• Clinical signs were consistent with ineffective hematopoiesis, despite normal or near-normal serum vitamin B12 and folic acid levels in one case.
• Neither case showed improvement following vitamin B12 supplementation, indicating limited therapeutic efficacy in these specific presentations.

Findings:

• Both dogs demonstrated significant dysplastic changes in bone marrow, confirming myelodysplastic syndrome.
• One dog's condition advanced to acute undifferentiated leukemia, observed during necropsy, highlighting the potential for malignant transformation.
• The hematologic disorder persisted for approximately five months in both cases, suggesting a chronic and progressive disease course.

Implications:

• These cases underscore the importance of recognizing myelodysplastic syndrome in veterinary diagnostics, particularly in dogs presenting with unexplained cytopenias and related clinical signs.
• The findings suggest that vitamin B12 deficiency may not be a primary driver in all canine MDS cases and that therapeutic responses can vary.
• Further research into the pathogenesis and treatment of canine myelodysplastic syndrome is warranted to improve diagnostic accuracy and therapeutic strategies.