Acquired hypocalciuric hypercalcemia in a dog

Area of Science:

• Veterinary Medicine
• Endocrinology
• Canine Health

Background:

• Hypercalcemia in dogs is often associated with primary hyperparathyroidism.
• Treatment for primary hyperparathyroidism may not resolve hypercalcemia in all cases.
• The calcium-sensing receptor (CaSR) plays a crucial role in calcium homeostasis.

Purpose of the Study:

• To investigate the cause of persistent hypercalcemia in a dog after parathyroidectomy.
• To identify potential autoimmune mechanisms contributing to hypercalcemia.
• To describe the first diagnosis of acquired hypocalciuric hypercalcemia in a canine patient.

Main Methods:

• Clinical evaluation including parathyroid hormone levels and imaging.
• Surgical parathyroidectomy and histopathological examination of parathyroid glands.
• Measurement of fractional calcium excretion.
• In vitro testing for autoantibodies against the canine calcium-sensing receptor (CaSR).

Main Results:

• The dog presented with asymptomatic hypercalcemia unresponsive to parathyroidectomy.
• Histopathology revealed parathyroid hyperplasia and hypertrophy.
• Fractional calcium excretion was low, suggesting a renal component.
• Autoantibodies against the CaSR were detected in the dog's serum.

Conclusions:

• The findings suggest acquired hypocalciuric hypercalcemia due to CaSR autoantibodies in this dog.
• This represents a novel cause of hypercalcemia in veterinary medicine.
• Further research is needed to understand the prevalence and implications of CaSR autoantibodies in dogs.