Parathyroid gland lesions in anurans are infrequently reported and most often occur secondary to experimental interventions. Husbandry-related parathyroid changes have not been documented in this order of Amphibia. Three American bullfrogs (Lithobates catesbeianus) living in a captive colony were euthanized due to clinical concern for metabolic bone disease secondary to lack of consistent dietary supplementation with vitamin D3. Necropsy revealed cystic dilation and variable proliferation of unidentified structures within the cranial coelom corresponding to the anatomical location of anuran parathyroid glands. Histologically, the structures consisted of sheets and whorls of elongated cells. Immunohistochemistry for pan-cytokeratin revealed strong cytoplasmic staining and Grimelius staining identified neuroendocrine granules in the elongated cells of these structures, supportive of a parathyroid origin.

Financial support was provided by the Department of Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University.

We thank the histopathology technicians, anatomic pathology residents and Laboratory Animal Resources staff for their contributions. Special thanks to Dr. Brittany Rasche, Dr. Andeliene Croce, Dr. Greg Lewbart and Kent Passignham for their diligent work and help with managing the clinical cases and post-mortem reports.

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