Gout in Primary Hyperparathyroidism, Connecting Crystals to the Minerals.

Musculoskeletal manifestations in primary hyperparathyroidism (PHPT) range from 13% to 93% encompassing pseudogout, vertebral fracture, myopathy, and cord compression. Though pseudogout has been the most prevalent musculoskeletal condition in PHPT, rarely reports of acute gouty attacks in large joints including the knee have been reported in the literature. Here we detail a unique case of PHPT presenting with acute severe bilateral knee joint inflammatory arthritis accompanied by occasional abdominal pain. Joint aspiration fluid study revealed extracellular monosodium urate crystals exhibiting strong negative birefringence on polarized light microscopy suggestive of acute gouty arthritis. Hypercalcemia and hypophosphatemia with high intact parathyroid hormone (iPTH) confirmed the diagnosis of PHPT and a right inferior parathyroid adenoma was localized. Parathyroidectomy resulted in statistically significant clinical improvement of the debilitating joint manifestations, and the patient was able to walk again without support. Although the incidence of gout is increasing because of an overall increase in metabolic syndrome prevalence, a higher prevalence than in the general population is reported in PHPT. Serum uric acid levels positively correlate with serum iPTH levels in PHPT, and parathyroidectomy leads to a reduction in levels. Acute inflammatory joint pain due to urate crystal deposition in a large joint like the knee is an uncommonly reported condition in PHPT. Identifying the correct etiology in such a case can result in marked clinical improvement in the joint manifestations following surgical cure of hyperparathyroidism.