Diffuse Idiopathic Skeletal Hyperostosis and Familial Hypocalciuric Hypercalcemia: A Unique Association in a Young Female

Familial hypocalciuric hypercalcemia (FHH) is a cause of lifelong hypercalcemia resulting from inactivated mutations in the calcium sensing receptor gene. Diffuse idiopathic skeletal hyperostosis (DISH) is an under diagnosed condition that leads to ossification of ligaments and entheses of the spine and peripheral skeleton. We describe a 45-year-old diabetic woman with hypercalcemia secondary to FHH who developed dysphagia because of external esophageal compression from DISH. The patient had no additional identifiable risk factors for DISH except for diabetes mellitus. An association between FHH and DISH has not been previously reported. Although most cases of hypercalcemia are found to have decreased bone mineralization, inactivation of calcium sensing receptor may induce a promitogenic response to hypercalcemia resulting in increased bone density. However, a causal association between FHH and DISH remains unproven.