Acute Inflammatory Arthropathy and Hypercalcemia Leading to a Diagnosis of Primary Hyperparathyroidism in a Patient With Known Sarcoidosis.

Calcium pyrophosphate deposition disease (CPPD) is a crystal-induced arthropathy characterized by calcium pyrophosphate crystal deposition in joints and soft tissues. The diagnosis is suggested by the presence of chondrocalcinosis on x-ray but is most often diagnosed by synovial fluid analysis (SFA). CPPD is associated with aging and metabolic disorders such as hyperparathyroidism. In this case, we present an 87-year-old woman with known sarcoidosis who presented with acute arthropathy, hypercalcemia, and radiographic evidence of CPPD. Her hypercalcemia had been attributed to her sarcoidosis in the past without a full workup. Hypercalcemia in the setting of suspected CPPD led to a full workup for hypercalcemia and ultimately led to a diagnosis of primary hyperparathyroidism. This case highlights the importance of a complete evaluation for hypercalcemia in the setting of CPPD, even when another disease, such as sarcoidosis, could explain hypercalcemia. Ultimately, CPPD aided in diagnosing hyperparathyroidism in our patient with known sarcoidosis.