SAT0442 CALCIUM PYROPHOSPHATE CRYSTAL ARTHRITIS DURING HOSPITALIZATIONS: A PROSPECTIVE, CRYSTAL-PROVEN CASE SERIES
Authors: Laura Ranieri, Francisca Sivera, Mariano Andrés
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background:</h3> Despite having passed more than fifty years after its initial description, essential questions for calcium pyrophosphate (CPP) crystal disease, such as clinical spectrum, diagnosis or management schemes, remain unsolved. Acute flares often occurred during hospitalizations. Scant reports have addressed this common setting for CPP crystal disease, and whether these patients behave similarly to ambulatory cases is unknown. <h3>Objectives:</h3> The aim of this work was to describe in a prospective way a crystal-proven case series of patients developing acute CPP crystal arthritis during hospitalizations for another conditions. <h3>Methods:</h3> An observational, cross sectional descriptive study was conducted in two Spanish centers from November 2013 to December 2018. A prospective convenience sampling was employed to select patients with crystal-proven CPP acute arthritis seen during hospital admissions. Demographic, clinical and CPP-related variables were collected, and X-rays (pelvis, knees, hands, affected joint when different) and laboratory tests (to rule out associated metabolic conditions) were systematically requested. A descriptive analysis is presented. <h3>Results:</h3> 90 episodes of acute CPP arthritis in 87 patients were seen in the study period, with an average age of 81.8 years (SD 7.7), 50.6% of them men. Approximately 26% of patients reported prior episodes of arthritis, most of them (68.4%) as outpatients. Only three patients were on preventive treatment for CPP arthritis (two on colchicine and one on low dose glucocorticoids). Regarding the acute CPP arthritis during admissions, they were predominantly monoarticular (81.0%) and the main involved joints were knee (46.0%), wrist (13.8%) and ankles (6.9%). The reasons for admission were diverse, with a mean of 7.7 days (SD 9.1) from admission to flare. About X-rays, 23.8% showed no chondrocalcinosis (CC) in the evaluated joints [61/80]. In 57.1% of patients there was chondrocalcinosis in the affected joint [44/77] and regarding usual joints: 74.3% in knees [55/74], 51.5% in triangular carpal ligament [34/66], 25.4% in metacarpo-phalangeal joints [17/67], 20% in pubic symphysis [14/70] and 17.6% in coxofemoral joints [12/68]. A secondary form of osteoarthritis was only seen in 10 patients (12.5%). About associated metabolic diseases, one case of primary hyperparathyroidism-related hypercalcemia and five cases of hypomagnesemia at the time of the flare were detected. In all six patients with a polyarticular presentation, laboratory tests for rheumatoid factor and ACPA were negative. <h3>Conclusion:</h3> From the findings of this prospective, crystal-proven series of CPP crystal arthritis in an intrahospital setting, we can remark: 1. The low numbers of previous ambulatory flares may suggest a different clinical entity of CPP disease. 2. Radiological CC was absent in around a quarter of patients despite a extensive assessment, so synovial fluid analysis remains essential for diagnosis. 3. The rarity of associated metabolic diseases seen runs against ruling out secondary causes of CPP disease in this setting. <h3>Disclosure of Interests:</h3> None declared