Background/Purpose: Despite more than fifty years after its initial description, key questions for calcium pyrophosphate (CPP) crystal disease, such as clinical spectrum, diagnosis or management schemes, remain unsolved. Acute flares often occurred during hospitalizations, but scant reports have addressed this common setting for CPP crystal disease. Whether these patients behave similarly to ambulatory cases is unknown. Our aim was to describe a prospective, crystal-proven case series of patients developing acute CPP crystal arthritis during hospitalizations for other conditions.

Methods: Observational, cross sectional descriptive study, conducted in two Spanish centers from November 2013 to December 2018. A prospective convenience sampling was used to select patients with crystal-proven CPP acute arthritis occurred during hospital admissions. Demographic, clinical and CPP-related variables were collected. X-rays of pelvis, knees, hands, and affected joint when different – to assess chondrocalcinosis (CC) – and laboratory tests – to rule out associated metabolic conditions – were systematically requested. A descriptive analysis is presented.

Results: We included 90 episodes of acute CPP arthritis in 87 patients, with an average age of 81.8 years (SD 7.7), 50.6% of them men. 26.4% of patients referred prior flares, most of them (68.4%) as outpatients. Three patients were on flare prophylaxis (colchicine in two, low-dose glucocorticoids in one). The reasons for admission were diverse, with a mean of 7.7 days (SD 9.1) from admission to flare. Flares were mostly monoarticular (81.0%) and involving knees (46.0%). In X-rays, 23.8% of patients showed absence of CC [61/80]; in 57.1%, CC was noted in the affected joint [44/77], while in 74.3% in knees [55/74], 51.5% in triangular carpal ligaments [34/66], 25.4% in metacarpophalangeal joints [17/67], 20% in pubic symphysis [14/70], and 17.6% in coxofemoral joints [12/68]. Secondary osteoarthritis was seen in 10 patients (12.5%). Hyperuricemia was noted in 12 patients (13.3%), hypomagnesemia at the time of the flare in five (5.7%), and one case of primary hyperparathyroidism was diagnosed. In all six patients with a polyarticular presentation, rheumatoid factor and ACPA were negative.

Conclusion: From this prospective, crystal-proven series of CPP crystal arthritis during hospitalizations, we can remark: i) the low numbers of prior flares as outpatients may suggest a different clinical entity; ii) CC was absent in around a quarter of patients despite an extensive assessment, so synovial fluid analysis remains essential for accurate diagnosis; and, iii) the rarity of associated metabolic diseases runs against systematic screening for secondary causes of CPP disease in this setting.

« Back to 2019 ACR/ARP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/calcium-pyrophosphate-crystal-arthritis-during-hospitalizations-a-prospective-crystal-proven-case-series/