Corneal mineralization as a presenting sign of primary hyperparathyroidism due to a parathyroid adenoma

To describe a bilateral corneal calcification presumed to be associated with primary hyperparathyroidism in a dog. Methods: An 8-year-old, male mongrel dog with bilateral corneal opacities was evaluated. Complete physical and ophthalmologic examination and laboratory work-up were performed. Results: Irregular, symmetrical corneal opacities in the central corneas were observed bilaterally. A small mass was detected on the left side of the neck, at the level of the thyroid gland. Serum ionic calcium concentration was 2.19 mmol/L (reference interval: 1.29-1.40 mmol/L),serum parathormone concentration was 12 pg/ml (reference interval: 10-44 pg/ml). This value was considered inappropriately high according to calcium concentration. Complete blood count, serum protein electrophoresis, coagulation test and urinalysis were normal. A computed tomography (CT) was performed to further characterize the mass of the neck and staging the patient. CT showed an enlargement with irregular shape of the left cranial parathyroid gland that was surgically removed. Histopathology revealed a rim of compressed parenchyma by an encapsulated, non-infiltrative neoplasm composed of packed cubical cells with eosinophilic cytoplasm. Neoplastic cells expressed chromogranin A and synaptophysin and they were negative for calcitonin and thyreoglobulin. An ophthalmologic diagnosis of a corneal calcification presumably caused by primary hyperparathyroidism due to a parathyroid adenoma was made. Postoperatively the serum calcium levels returned to normal. However, after observation for 1.5 years the corneal opacities, although not increased, were unchanged. Conclusions: Calcific keratopathy has been associated with systemic hypercalcemia. In our case this keratopathy was the presenting sign that allowed to diagnose the underlying endocrine disease.