Hypercalcemia and Lytic Bone Lesions Masquerading Inflammatory Arthritis Treated as Rheumatoid Arthritis

Hyperparathyroidism is a complex clinical syndrome characterized by dysfunction in the metabolism of bone, calcium and phosphorus. Rheumatologic manifestations are common amongst patients with hyperparathyroidism. We report a 50-year-old woman with hypercalcemia, lytic bone lesions and inflammatory arthritis of both hands that were not resolved after parathyroidectomy. Laboratory evidence of elevated erythrocyte sedimentation rate, positive C-reactive protein (CRP) and high titers of anti-CCP and rheumatoid factor was diagnostic of rheumatoid arthritis (RA) according to European League Against Rheumatism criteria. Eventually, with the concomitant diagnoses of hyperparathyroidism and RA, she was treated with methotrexate and hydroxychloroquin. Hyperparathyroidism may present with rheumatologic manifestations, leading to an initial misdiagnosis. Furthermore, attention to this fact that hypercalcemia is not commonly associated with RA, and rather suggestive of a concomitant disorder, is crucial to the diagnosis of hyperparathyroidism in RA patients with hypercalcemia.