Hyperparathyroidism in a Patient with Autoimmune Polyglandular Syndrome

Autoimmune hypercalcemia has been reported in only a few cases, and never in the context of autoimmune polyglandular syndrome. A patient with type 1, insulin-dependent diabetes mellitus, Graves' disease, and antiparietal cell antibodies presented with persistent hypercalcemia with inappropriate PTH secretion. Other causes of hypercalcemia were excluded. In this context of two associated organ-specific autoimmune diseases we searched for autoantibodies directed to parathyroid tissue and to calcium-sensing receptor. Anti-parathyroid autoantibodies were detected by indirect immunofluorescence on parathyroid adenomas, and autoantibody against a peptide of the extracellular domain of the calcium-sensing receptor were detected by immunoblotting. Autoimmune hypercalcemia may be another organ-specific feature of autoimmune polyglandular syndrome.