Risk factors for pseudogout in the general population

Calcium Pyrophosphate Crystal Deposition: Insights to Risks Factors and Associated Conditions

PURPOSE OF THE REVIEW

This review provides an overview of medical conditions and risk factors associated with CPPD.

RECENT FINDINGS

Recent studies have indicated that CPPD patients may have a higher risk for systemic conditions such as cardiovascular diseases. Calcium pyrophosphate deposition disease (CPPD) is a common crystal arthropathy that primarily affects older adults, and, in most cases, the aetiology is idiopathic. Age is the most remarkable risk factor and due to the aging population, the prevalence of this condition is expected to increase. Strong evidence supports an association between CPPD and several metabolic and endocrine conditions, including hemochromatosis, hyperparathyroidism, hypomagnesemia, and hypophosphatasia. Additionally, there is growing evidence of an increased risk for cardiovascular diseases among CPPD patients, alongside potential links to rheumatic disorders, gender, medications, and joint trauma. Further research is needed to explore the underlying mechanisms linking CPPD to associated conditions and to develop targeted therapies with the aim of improving patient outcomes.

Cervical Spine Myelopathy Caused by Calcium Pyrophosphate Dihydrate Deposition of the Ligamentum Flavum: A Case Report

Calcium pyrophosphate dihydrate deposition (CPPD), commonly known as pseudogout, is an inflammatory arthropathy primarily affecting the knee, wrist, hip, and shoulder joints. However, it can occasionally deposit in various structures surrounding the spinal column, including the facet joints, ligamentum flavum, bursae, and intervertebral discs. Such occurrences are typically asymptomatic or associated with mild neck pain. Nonetheless, severe cases may lead to myeloradiculopathy, characterized by severe neck pain and upper extremity weakness. Conservative management with nonsteroidal anti-inflammatory drugs is often sufficient for mild cases, while surgical decompression remains the gold standard for severe cases with significant spinal cord compression. Herein, we present a rare case of pseudogout, manifesting as cervical spine myelopathy due to calcium pyrophosphate dihydrate deposition in the ligamentum flavum and facet joints at C1-2. This was found incidentally during cervical spine decompression and fusion and subsequentially confirmed through pathological examination. Following the removal of the compressive pathology, the patient reported significant improvements in neck pain and neurological symptoms. This case underscores the importance of considering pseudogout in the differential diagnosis of acute neck pain presenting with myelopathy or radiculopathy.

Calcium pyrophosphate deposition disease

Calcium pyrophosphate deposition (CPPD) disease is a consequence of the immune response to the pathological presence of calcium pyrophosphate (CPP) crystals inside joints, which causes acute or chronic inflammatory arthritis. CPPD is strongly associated with cartilage degradation and osteoarthritis, although the direction of causality is unclear. This clinical presentation is called CPPD with osteoarthritis. Although direct evidence is scarce, CPPD disease might be the most common cause of inflammatory arthritis in older people (aged >60 years). CPPD is caused by elevated extracellular-pyrophosphate concentrations in the cartilage and causes inflammation by activation of the NLRP3 inflammasome. Common risk factors for CPPD disease include ageing and previous joint injury. It is uncommonly associated with metabolic conditions (eg, hyperparathyroidism, haemochromatosis, hypomagnesaemia, and hypophosphatasia) and genetic variants (eg, in the ANKH and osteoprotegerin genes). Apart from the detection of CPP crystals in synovial fluid, imaging evidence of CPPD in joints by mainly conventional radiography, and increasingly ultrasonography, has a central role in the diagnosis of CPPD disease. CT is useful in showing calcification in axial joints such as in patients with crowned dens syndrome. To date, no treatment is effective in dissolving CPP crystals, which explains why control of inflammation is currently the main focus of therapeutic strategies. Prednisone might provide the best benefit-risk ratio for the treatment of acute CPP-crystal arthritis, but low-dose colchicine is also effective with a risk of mild diarrhoea. Limited evidence suggests that colchicine, low-dose weekly methotrexate, and hydroxychloroquine might be effective in the prophylaxis of recurrent flares and in the management of persistent CPP-crystal inflammatory arthritis. Additionally, biologics inhibiting IL-1 and IL-6 might have a role in the management of refractory disease.

Anakinra for Refractory Pseudogout in Patients with End-stage Renal Disease on Haemodialysis

Calcium pyrophosphate deposition (CPPD) arthritis is the second most common type of crystal-induced arthritis after gout. Acute flares are commonly treated with non-steroidal anti-inflammatory drugs, intra-articular or short-term systemic glucocorticoids or colchicine. However, since there is no pharmacological treatment to reduce CPPD crystal burden, relapsing or chronic CPPD arthritis may be challenging to treat, particularly in patients with end-stage renal disease who are at risk for toxicity of the above medications. Since IL-1β appears to be driving CPPD arthritis, we treated two patients with chronic CPPD arthritis and end-stage renal disease on haemodialysis with the IL-1β receptor antagonist anakinra. In both patients, arthritis resolved quickly, while continuation of anakinra maintained remission and allowed complete glucocorticoid withdrawal. Therefore, anakinra may be a safe and effective option both for short and long-term treatment of CPPD arthritis in patients on chronic renal replacement therapy.

Diagnosis and Treatment of Calcium Pyrophosphate Deposition (CPPD) Disease: A Review

Calcium Pyrophosphate Dihydrate (CPPD) crystal-related arthropathies are a common cause of acute and chronic arthritis caused by the deposition of calcium pyrophosphate crystals in joints and soft tissues, resulting in inflammation and joint damage. They present with a wide spectrum of clinical manifestations and often present challenges to diagnosis and management as they commonly affect older co-morbid patients. The challenges are compounded by a lack of a well-defined description of CPPD. However, an international expert-driven process is underway to develop CPPD classification criteria. Treatment is also problematic as unlike gout, there are no agents available that decrease the crystal burden. Treatment options have often been extrapolated from gout treatment pathways without having extensive trials or a solid evidence base. It is hoped the new CPPD classification guidelines will contribute to large multicentre studies, with well-defined patient cohorts, which will facilitate the production of high-quality evidence to guide the management of this condition. Here, we discuss the barriers and facilitators in diagnosing and treating CPPD-related arthropathy.

Confirming Prior and Identifying Novel Correlates of Acute Calcium Pyrophosphate Crystal Arthritis

OBJECTIVE

To investigate previously identified and novel correlates of acute calcium pyrophosphate (CPP) crystal arthritis among well-characterized cases.

METHODS

In this case-control study, we identified cases of acute CPP crystal arthritis using a validated algorithm (positive predictive value 81%) applied in the Partners HealthCare electronic health record (EHR). Cases were matched to general patient controls on the year of first EHR encounter and index date. Prespecified potential correlates included sex, race, and comorbidities and medications previously associated with CPP deposition/acute CPP crystal arthritis in the literature. We estimated odds ratios (ORs) and 95% confidence intervals using conditional logistic regression models adjusted for demographic characteristics, comorbidities, medications prescribed in the past 90 days, health care utilization, and multimorbidity score.

RESULTS

We identified 1,697 cases matched to 6,503 controls. Mean ± SD age was 73.7 ± 11.8 years, 56.7% were female, 80.8% were White, and 10.3% were Black. All prespecified covariates were more common in cases than controls. Osteoarthritis (OR 3.08), male sex (OR 1.35), rheumatoid arthritis (OR 2.09), gout (OR 2.83), proton pump inhibitors (OR 1.94), loop diuretics (OR 1.60), and thiazides (OR 1.46) were significantly associated with acute CPP crystal arthritis after full adjustment. Black race was associated with lower odds for acute CPP crystal arthritis compared to White race (OR 0.47).

CONCLUSION

Using a validated algorithm to identify nearly 1,700 patients with acute CPP crystal arthritis, we confirmed important correlates of this acute manifestation of CPP deposition. This is the first study to report higher odds for acute CPP crystal arthritis among males.

Gout Prevalence, Practice Patterns, and Associations with Outcomes in North American Dialysis Patients

INTRODUCTION

Gout occurs frequently in patients with kidney disease and can lead to a significant burden on quality of life. Gout prevalence, and its association with outcomes in hemodialysis (HD) and peritoneal dialysis (PD) populations located in North America, is unknown.

METHODS

We used data from North America cohorts of 70,297 HD patients (DOPPS, 2012-2020) and 5117 PD patients (PDOPPS, 2014-2020). We used three definitions of gout for this analysis: (1) having an active prescription for colchicine or febuxostat; (2) having an active prescription for colchicine, febuxostat, or allopurinol; or (3) having an active prescription for colchicine, febuxostat, or allopurinol, or prior diagnosis of gout. Propensity score matching was used to compare outcomes among patients with versus without gout. Outcomes included erythropoietin resistance index (ERI=erythropoiesis stimulating agent dose per week/(hemoglobin×weight)), all-cause mortality, hospitalization, and patient-reported outcomes (PROs).

RESULTS

The gout prevalence was 13% in HD and 21% in PD; it was highest among incident dialysis patients. Description of previous history of gout was rare, and identification of gout defined by colchicine (2%-3%) or febuxostat (1%) prescription was less frequent than by allopurinol (9%-12%). Both HD and PD patients with gout (versus no gout) were older, were more likely male, had higher body mass index, and had higher prevalence of cardiovascular comorbidities. About half of patients with a gout history were prescribed urate-lowering therapy. After propensity score matching, mean ERI was 3%-6% higher for gout versus non-gout patients while there was minimal evidence of association with clinical outcomes or PROs.

CONCLUSION

In a large cohort of PD and HD patients in North America, we found that gout occurs frequently and is likely under-reported. Gout was not associated with adverse clinical or PROs.

Proton-Pump Inhibitors and Risk of Calcium Pyrophosphate Deposition in a Population-Based Study

OBJECTIVE

There are no proven effective medical treatments to prevent calcium pyrophosphate crystal deposition (CPPD). Hypomagnesemia is a known CPPD risk factor. The present study was undertaken to carry out a real-world epidemiologic study on proton-pump inhibitor (PPI) use, which can cause hypomagnesemia, and CPPD risk.

METHODS

We conducted a time-stratified, propensity score (PS)-matched cohort study using the UK-based IQVIA Medical Research Data. We compared risk of incident CPPD among PPI users versus H2 blocker users using Cox proportional hazards models. We used greedy matching of incident PPI users 1:1 to incident histamine receptor 2 (H2 ) blocker users in 1-year cohort accrual blocks. Subjects were censored at time of drug switch. We evaluated incident use of PPI and H2 blockers prior to incident CPPD using a nested case-control study within the same cohort, matched 1:4 by age and sex using risk-set sampling.

RESULTS

We identified 81,102 PPI and H2 blocker initiators, with 113 and 63 incident cases of CPPD, respectively. In the case-control study when compared with nonusers, both PPI and H2 B users had higher risk of incident CPPD, with odds ratios (ORs) of 1.79 (95% confidence interval [95% CI] 1.55-2.07) and 1.52 (95% CI 1.14-2.03), respectively. Incident PPI use was nonsignificantly associated with incident CPPD (hazard ratio 1.03 [95% CI 0.75-1.41]) compared with H2 blocker use.

CONCLUSION

In this study using real-world data, incident use of PPIs was not associated with a higher risk of CPPD compared with incident H2 blocker use, although use of PPI and H2 blockers had higher risk compared with nonuse.

Effects of colchicine use on ischemic and hemorrhagic stroke risk in diabetic patients with and without gout

This study aimed to determine the effect of colchicine use on the risk of stroke among patients with diabetes mellitus (DM). We retrospectively enrolled patients with DM between 2000 and 2013 from the Longitudinal Health Insurance Database and divided them into a colchicine cohort (n = 8761) and noncolchicine cohort (n = 8761) by using propensity score matching (PSM). The event of interest was a stroke, including ischemic stroke and hemorrhagic stroke. The incidence of stroke was analyzed using multivariate Cox proportional hazards models between the colchicine cohort and the comparison cohort after adjustment for several confounding factors. The subdistribution hazard model was also performed for examination of the competing risk. The colchicine cohort had a significantly lower incidence of stroke [adjusted hazard ratios (aHR), 95% confidence intervals (95%CI)] (aHR = 0.61, 95%CI = 0.55–0.67), ischemic stroke (aHR = 0.59, 95%CI = 0.53–0.66), and hemorrhagic stroke (aHR = 0.66, 95%CI = 0.53–0.82) compared with the noncolchicine cohort. Drug analysis indicated that patients in the colchicine cohort who received colchicine of cumulative daily defined dose (cDDD) > 14 and duration > 28 days had a lower risk of stroke and ischemic stroke compared with nonusers. The colchicine cohort (cDDD > 150, duration > 360 days) also had a lower risk of stroke, ischemic stroke, and hemorrhagic stroke. The cumulative incidence of stroke, ischemic stroke, and hemorrhagic stroke in the colchicine cohort was significantly lower than that in the noncolchicine cohort (log-rank P < 0.001). However, the subdistribution hazard model reveal the colchicine was not associated with the hemorrhagic stroke in DM patients without gout (aHR = 0.69, 95%CI = 0.47–1.00). Colchicine use with cDDD > 14 and duration > 28 days was associated with lower risk of stroke and ischemic stroke, and colchicine use with cDDD > 150 and duration > 360 days played an auxiliary role in the prevention of stroke, ischemic stroke, and hemorrhagic stroke in patients with DM. The colchicine for the hemorrhagic stroke in DM patients without gout seem to be null effect.

Outcomes and resource utilization in calcium pyrophosphate deposition disease patients who underwent total knee arthroplasty: a cross-sectional analysis

This cross-sectional study aims to evaluate the predictors, outcomes, and resource utilization of total knee arthroplasty (TKA) in calcium pyrophosphate deposition disease (CPPD) patients. We used the US National Inpatient Sample database to identify CPPD and non-CPPD who underwent TKA from 2006 to 2014. Data collection included patient demographics and comorbidities. Outcomes following TKA included in-hospital mortality, complications, length of hospitalization, hospital charges, and disposition. Among the 5,564,005 patients who have undergone TKA, 11,529 (0.20%) had CPPD, with a median age of 72 years, and 53.7% were females. Compared with non-CPPD, patients with CPPD were more likely to be older (mean 72 vs 66 years; p < 0.001), male, white, and have Medicare insurance. CPPD patients were more likely to have ≥ 2 comorbidities calculated by the Charlson Comorbidity Index and discharge to an inpatient/rehabilitation facility. Regarding inpatient complications, myocardial infarction and knee reoperation were significantly more common in CPPD patients. TKA in CPPD patients was associated with significantly higher odds of increased length of stay (> 3 days) than those without CPPD (OR 1.43, 95% CI 1.37-1.49). There was no significant difference in the in-hospital mortality even after adjusting for possible confounders. CPPD patients who underwent TKA were more likely to have a longer hospital stay and discharge to a non-home setting than non-CPPD. Also, CPPD patients had a higher comorbidity burden and risk for myocardial infarction and reoperation.Key Points• This is the largest study to analyze data of CPPD patients who underwent TKA and compare them with non-CPPD patients, using a large nationwide database.• Compared to non-CPPD patients, TKA in CPPD patients is associated with a greater length of stay and disposition to a nursing/rehabilitation facility.• In-hospital complications such as myocardial infarction and reoperation were more frequently observed in CPPD patients than non-CPPD.• The results of this study should alert healthcare providers to develop strategies in order to improve outcomes of CPPD patients undergoing TKA.

Review: Outcome measures in calcium pyrophosphate deposition

This review highlights outcomes for patients with calcium pyrophosphate deposition (CPPD) reported in prior studies and underscores challenges to assessing outcomes of this condition. Prior clinical studies of interventions for CPPD focused on joint damage and calcification on imaging tests, joint pain, swelling, and inflammatory biomarkers. Qualitative interviews with patients with CPPD and healthcare providers additionally identified flares, overall function, and use of analgesic medications as important outcomes. Imaging evidence of joint damage and calcification is likely to be outcomes in future clinical studies of CPPD, though reliability and sensitivity to change in CPPD require further testing for several imaging modalities. Challenges to outcome measurement in CPPD include questions of attribution of signs and symptoms to CPPD versus co-existing forms of arthritis, lack of therapies to prevent or dissolve calcium pyrophosphate crystal deposition, absence of validated patient- or physician-reported CPPD outcome measures, and scarcity of large cohorts in which to study outcomes of different clinical presentations of CPPD.

The Association of Diuretics and Proton Pump Inhibitors With Chondrocalcinosis

Objective

Hypomagnesemia increases the risk of chondrocalcinosis and calcium pyrophosphate disease. We examined whether the use of drugs that can cause hypomagnesemia, diuretics and proton pump inhibitors (PPIs), increases the risk of chondrocalcinosis.

Methods

Participants in the Multicenter Osteoarthritis (MOST) Study obtained weight‐bearing knee radiographs, and their medication use was recorded at baseline and 30‐, 60‐, 84‐, and 144‐month examinations. We read radiographs serially for chondrocalcinosis and characterized incident chondrocalcinosis when it first appeared. We classified diuretic use as thiazide, loop, and other. To test drug effects on incident chondrocalcinosis at each interval (eg, 30‐60 months), we excluded persons with chondrocalcinosis at the interval’s beginning. For each drug, we evaluated exposure at the beginning and end of the interval. We conducted knee‐based analyses using Bayesian mixed‐effects discrete time survival models adjusted for age, sex, body mass index, radiographic osteoarthritis, race, and clinic site.

Results

Of 5272 knees, 196 developed chondrocalcinosis. Thiazide use (21.7% of examinations) and PPI use (13.7%) were common. Neither loop nor other diuretic use was associated with incident chondrocalcinosis. Thiazide use at the beginning and end of the interval of incidence conferred a high risk (hazard ratio [HR] = 2.18; 95% confidence interval [CI] 1.23‐3.89), but use at the beginning of the interval was not associated with risk (HR = 1.04). PPI use at the interval’s beginning increased risk of chondrocalcinosis (HR = 2.29; 95% CI 1.37‐3.79).

Conclusion

Thiazide diuretics, but not other diuretics, and PPI use probably increase the risk of chondrocalcinosis. These findings may have important clinical implications.

Cervical myeloradiculopathy as an initial presentation of pseudogout

Pseudogout, also known as calcium pyrophosphate deposition disease, is an inflammatory arthropathy that primarily occurs in the peripheral joints, such as the knee or elbow. Spinal pseudogout is uncommon, and neck pain is its most common clinical manifestation. However, cervical myeloradiculopathy as an initial presentation of pseudogout attack of the ligamentum flavum has rarely been reported in the literature. We report a case of a 65-year-old woman who presented with neck pain, bilateral finger numbness, and left-sided upper extremity weakness. Magnetic resonance images showed an epidural mass at the C4–5 level, compressing the spinal cord. Following laminectomy with removal of the calcified mass, the profound neurologic deficits gradually recovered. A pathological examination confirmed the diagnosis of cervical pseudogout.

Classifying Pseudogout Using Machine Learning Approaches With Electronic Health Record Data

OBJECTIVE

Identifying pseudogout in large data sets is difficult due to its episodic nature and a lack of billing codes specific to this acute subtype of calcium pyrophosphate (CPP) deposition disease. The objective of this study was to evaluate a novel machine learning approach for classifying pseudogout using electronic health record (EHR) data.

METHODS

We created an EHR data mart of patients with ≥1 relevant billing code or ≥2 natural language processing (NLP) mentions of pseudogout or chondrocalcinosis, 1991-2017. We selected 900 subjects for gold standard chart review for definite pseudogout (synovitis + synovial fluid CPP crystals), probable pseudogout (synovitis + chondrocalcinosis), or not pseudogout. We applied a topic modeling approach to identify definite/probable pseudogout. A combined algorithm included topic modeling plus manually reviewed CPP crystal results. We compared algorithm performance and cohorts identified by billing codes, the presence of CPP crystals, topic modeling, and a combined algorithm.

RESULTS

Among 900 subjects, 123 (13.7%) had pseudogout by chart review (68 definite, 55 probable). Billing codes had a sensitivity of 65% and a positive predictive value (PPV) of 22% for pseudogout. The presence of CPP crystals had a sensitivity of 29% and a PPV of 92%. Without using CPP crystal results, topic modeling had a sensitivity of 29% and a PPV of 79%. The combined algorithm yielded a sensitivity of 42% and a PPV of 81%. The combined algorithm identified 50% more patients than the presence of CPP crystals; the latter captured a portion of definite pseudogout and missed probable pseudogout.

CONCLUSION

For pseudogout, an episodic disease with no specific billing code, combining NLP, machine learning methods, and synovial fluid laboratory results yielded an algorithm that significantly boosted the PPV compared to billing codes.

The Incidence and Significance of Calcium Pyrophosphate Dihydrate Deposits in Histologic Examinations of Total Hip, Knee, and Shoulder Joint Arthroplasties

CONTEXT.—

The incidence, distribution, and significance of calcium pyrophosphate dihydrate deposition (CPPD) disease have not been extensively compared among various total joint resections.

OBJECTIVE.—

To investigate and define the clinical and pathologic features of CPPD in hip, shoulder, and knee arthroplasties.

DESIGN.—

We retrospectively reviewed consecutive total hip, knee, and shoulder arthroplasty cases (N = 3195) confirmed pathologically between January 1, 2017, and October 10, 2018, comparing clinical and pathologic data.

RESULTS.—

Among 2004 hip arthroplasties, 61 (3%) had CPPD on pathologic examination; the majority had a histologic diagnosis of osteoarthritis followed by fracture and avascular necrosis. Of 1113 knee arthroplasties, 98 (9%) had CPPD; all had a histologic diagnosis of osteoarthritis. Among 78 shoulder arthroplasties, 10 (13%) had CPPD; all but one had a histologic diagnosis of osteoarthritis. Patients with hip and knee CPPD were significantly older than those without CPPD. Of the 169 pathologically detected CPPD cases, only 35 (21%) were documented on preoperative radiologic images or by other clinical means; radiology reports were significantly more likely to document chondrocalcinosis in the knees than in the hips. Histologically, CPPD were noted almost exclusively in the separately submitted soft tissues/joint capsule, concomitantly involving the articular cartilage surface in only 3.0% (5 of 169) of cases.

CONCLUSIONS.—

Calcium pyrophosphate dihydrate deposition is more than twice as likely to occur in the knees and shoulders compared with the hips. Patients with CPPD in the knees or hips are usually not recognized preoperatively/radiologically and constitute a significantly older population. Reliably establishing the diagnosis of CPPD requires pathologic examination of the submitted soft tissue/joint capsule.

Calcium pyrophosphate deposition disease: A case report with bilateral involvement of the temporomandibular joints and concurrence of psoriatic arthritis

Calcium pyrophosphate dehydrate deposition (CPDD) disease very rarely affects the temporomandibular joint (TMJ). It may resemble synovial chondromatosis, chondrosarcoma, chondroblastoma, or a parotid tumor. Clinical examination, CT, and MRI are important in making the correct diagnosis. Surgical removal of CPDD is necessary with or without excision of the TMJ.

Acute Calcium Pyrophosphate Crystal Arthritis Flare Rate and Risk Factors for Recurrence

OBJECTIVE

Little is known about acute calcium pyrophosphate (CPP) crystal arthritis flare rates and risk factors for recurrence. We characterized flares and determined the rate and predictors of acute CPP crystal arthritis flares in an academic medical center cohort.

METHODS

We performed a retrospective cohort study among a random sample of patients with acute CPP crystal arthritis identified in the Partners HealthCare electronic medical record, 1991-2017. Flare was defined as self-limited, acute-onset synovitis with synovial fluid CPP crystals and/or chondrocalcinosis, not better explained by another cause. We calculated incidence rates (IR) for acute CPP crystal arthritis flare among all subjects and by sex. We estimated HR for recurrent flare using univariate Cox models that accounted for within-person correlated data.

RESULTS

We identified 70 patients with acute CPP crystal arthritis with a total of 111 flares. Recurrent flares occurred in 24% of patients; half of flares occurred in a previously unaffected joint. The acute CPP crystal arthritis flare rate was 11.4 per 100 person-years overall (95% CI 8.2-15.4), 14.2 in women (95% CI 9.6-0.1), and 7.1 in men (95% CI 3.4-13.0). Cancer (HR 2.98, 95% CI 1.33-6.68) and chronic kidney disease (HR 2.92, 95% CI 1.10-7.76) were associated with a higher rate for recurrent flare.

CONCLUSION

Recurrent flares occurred in about one-fourth of patients with acute CPP crystal arthritis and often occurred in previously unaffected joints. The acute CPP crystal arthritis flare rate was twice as high in women as in men.

Issues in CPPD Nomenclature and Classification

PURPOSE OF REVIEW

This paper covers confusion and challenges in the nomenclature of calcium pyrophosphate deposition disease. Clinicians, investigators, and patients are faced with a variety of terms that are used to describe CPPD and its phenotypes, and clarity is greatly needed to help advance research and patient care. Motivation for the upcoming development of CPPD classification criteria is reviewed.

RECENT FINDINGS

EULAR proposed recommended terminology for CPPD in 2011. International Classification of Diseases (ICD-9 and ICD-10) billing codes identify definite or probable CPPD with variable accuracy depending on the clinical setting and comparator group. READ diagnostic codes have been employed to identify pseudogout in UK datasets but their accuracy has not been evaluated. CPPD classification criteria will provide a system for identifying a relatively homogenous group of patients to be included in clinical studies, enabling comparison of outcomes across studies. CPPD nomenclature remains challenging for clinicians, investigators, and patients. A lay-friendly definition of CPPD, using easily accessible terminology, would be welcome. CPPD classification criteria are a necessary step in moving forward CPPD clinical research and may involve a range of clinical, laboratory, and imaging modalities.

First Presentation of Acute Pseudogout Following Total Knee Replacement

Introduction:

Infection of a total knee replacement (TKR) is a very serious complication of knee arthroplasty surgery as the repercussions for the patient often include long-term antibiotics, further surgery, revision surgery, and worse outcomes in the long-term including increased morbidity and mortality. As such, the careful assessment of a patient presenting with an acutely inflamed TKR is of paramount importance.

Case Report:

We report a case of a patient presenting with the clinical signs and symptoms of an acute infection of their TKR. The patient was ultimately diagnosed as having pseudogout.

Conclusion:

This case illustrates that crystal arthropathy must be one of the differential diagnoses for a suspected infection of a TKR, as failure to recognize this may result in unnecessary and detrimental treatment.

Patients Presenting with a Hot, Swollen Joint: A Single-Centre Retrospective Analysis

BACKGROUND

A hot, swollen joint is a common clinical condition encountered in the ED and elective orthopaedic and rheumatology clinics. These patients can be difficult to manage and properly treat.

AIMS AND OBJECTIVES

The aim of this study was to report a single centre retrospective analysis of patients presenting to our institution for a hot, swollen joint over a three-month period.

METHODS

The study included patients presenting with a hot, swollen joint to ED or electively to clinics. The synovial fluid was aspirated and sent for microbiological and cytological investigation. P value was set to < 0.001. 36 patients (22 M, 14 F) with a mean age of 72.8 ± 17.4 years met our criteria. 20 cases (55.6 %) involved the knee joint, the wrist in 10 cases (27.8%), the elbow in 3 cases (8.3%) and the shoulder in 3 cases (8.3%).

RESULTS

Of the 36 synovial fluid samples collected, only 7 (19.4%) reported evidence of infection. On cytological examination of the synovial fluid, 21 (58.3%) reported presence of calcium pyrophosphates crystals (Pseudogout), 4 (11.1 %) reported presence of uric acid crystals (Gout) and 11 (30.5%) reported absence of crystals. We found a significant correlation between age and the diagnosis of pseudogout and between previous antibiotic treatment and ED presentation. Our study sheds light on the high incidence of crystal-related pathologies.

CONCLUSION

In order to improve our management of this common condition and enhance our understanding of the clinical diagnosis in certain patient population, further high-profile clinical studies are needed.

Pseudogout: An Autoimmune Paraneoplastic Manifestation of Myelodysplastic Syndrome

Myelodysplastic syndrome (MDS) is often associated with autoimmune paraneoplastic manifestations. Seronegative arthritis is among one of them. Very rarely, pseudogout demonstrated as paraneoplastic autoimmune manifestations of MDS has been adumbrated so far. Our case would be the another addition in the series. Our patient is an 83-year-old male lately diagnosed with MDS. After six months of initial diagnosis, he had a sudden onset episode of pain and swelling involving left wrist. Synovial fluid analysis from respective radiocarpal joint confirmed the presence of intracellular positively birefringent rhomboid shaped crystals of calcium pyrophosphate dihydrate (CPPD). This was followed by another two flares of pseudogout involving right knee and lumbar spine at separate time intervals. Each of the episodes mentioned above responded well to intravenous and oral steroids. After the third bout, he was started treatment with azacitidine which showed effective abatement of further episodes of pseudogout up until now.

Pseudogout among Patients Fulfilling a Billing Code Algorithm for Calcium Pyrophosphate Deposition Disease

To test the performance of a billing claims-based calcium pyrophosphate deposition disease (CPPD) algorithm for identifying pseudogout. We applied a published CPPD algorithm at an academic institution and randomly selected 100 patients for electronic medical record review for 3 phenotypes: (1) definite/probable CPPD, (2) definite/probable pseudogout; (3) definite pseudogout. Clinical data were recorded and positive predictive value (PPV) (95% CI) for each phenotype was calculated. We then modified the published algorithm to require ≥ 1 of 4 relevant terms ("pseudogout", "calcium pyrophosphate crystals", "CPPD", or "chondrocalcinosis") through automated text searching in clinical notes, and re-calculated PPVs. To estimate the percentage of pseudogout patients not identified by the published algorithm, we reviewed a random sample of 50 patients with ≥ 1 of 4 relevant terms in clinical notes who did not fulfill the published algorithm. Among patients fulfilling the published algorithm, 68% had ≥ 1 of 3 phenotypes. The published algorithm had PPV 24.0% (95% CI 19.3-28.7%) for definite/probable pseudogout and 18.0% (95% CI 14.5-21.5%) for definite pseudogout. Requiring ≥ 1 of 4 relevant terms in clinical notes increased PPV to 33.3% (95% CI 26.8-39.8%) for definite/probable pseudogout and 24.6% (95% CI 19.8-29.4%) for definite pseudogout. Among patients not fulfilling the published algorithm, 16.0% had definite/probable pseudogout and 6.0% had definite pseudogout. A billing code-based CPPD algorithm had low PPV for identifying pseudogout. Adding text searching modestly enhanced the PPV, though it remained low. These findings highlight the need for improved approaches to identify pseudogout to facilitate epidemiologic studies.

Concurrence of rheumatoid arthritis and calcium pyrophosphate deposition disease: A case collection and review of the literature

OBJECTIVE

Calcium pyrophosphate deposition disease (CPDD) is arthritis caused by calcium pyrophosphate (CPP) crystal deposition in joints. It is commonly associated with aging as well as a handful of metabolic syndromes. Recent epidemiologic studies suggest a positive association of CPDD and rheumatoid arthritis (RA). Yet how these diseases are related remains unclear. We set out to describe 21 well-characterized patients with both diagnoses.

METHODS

Medical records of patients with both RA and CPDD identified at a single academic practice site were reviewed for age, gender, age of CPDD and RA onset, disease duration, joint involvement, and lab values including rheumatoid factor (RF), cyclic citrullinated peptide antibody (CCP), iron studies, and parathyroid hormone and calcium levels.

RESULTS

The mean age of CPDD onset was 69.5 ± 11.4 years, with a mean RA age onset of 53.9 ± 16 years, demonstrating a mean lag of 13.4 ± 10.9 years between diagnoses. The majority of RA patients were diagnosed with CPDD based on the presence of radiographic chondrocalcinosis (15/21). The most commonly involved joint was the knee, followed by the wrist, hip, and shoulder.

CONCLUSIONS

These data show that the diagnosis of RA often precedes the diagnosis of CPDD. This asynchronous presentation taken together with the classic age of onset for CPDD and typical pattern of joint involvement supports the hypothesis that CPDD develops in RA patients through similar processes as those that cause the idiopathic forms of this disease.

Calcium Pyrophosphate Deposition Disease and Associated Medical Comorbidities: A National Cross-Sectional Study of US Veterans

OBJECTIVE

Calcium pyrophosphate deposition disease (CPDD) is a common cause of acute and chronic arthritis, yet there are few large epidemiologic studies of CPDD. We sought to characterize CPDD in the national Veterans Affairs (VA) population.

METHODS

Using data from the Department of VA Corporate Data Warehouse, patients with International Classification of Diseases, Ninth Revision, codes for CPDD seen at any VA medical center from 2010 through 2014 were matched by age and sex with control patients without CPDD. We used multivariate analysis to compare the prevalence and odds ratios (ORs) of various comorbidities, substance use, medication exposures, and arthroplasties among patients with and without CPDD.

RESULTS

We identified 25,157 patients with CPDD, yielding a point prevalence of 5.2 per 1,000. The mean ± SD age was 68.1 ± 12.3 years, and 95% were male. The strongest positive associations with CPDD were hyperparathyroidism (OR 3.35 [95% confidence interval (95% CI) 2.96-3.79]), gout (OR 2.82 [95% CI 2.69-2.95]), osteoarthritis (OR 2.26 [95% CI 2.15-2.37]), rheumatoid arthritis (OR 1.88 [95% CI 1.74-2.03]), and hemochromatosis (OR 1.87 [95% CI 1.57-2.24]). Positive associations were also seen with higher odds for osteoporosis (OR 1.26 [95% CI 1.16-1.36]), hypomagnesemia (OR 1.23 [95% CI 1.16-1.30]), chronic kidney disease (OR 1.12 [95% CI 1.07-1.18]), and calcium supplementation (OR 1.15 [95% CI 1.06-1.24). Negative associations were seen with proton-pump inhibitors (OR 0.58 [95% CI 0.55-0.60]) and loop diuretics (OR 0.80 [95% CI 0.76-0.84]).

CONCLUSION

Using a large national data set, we confirmed known associations with CPDD, provided support for positive associations with rheumatoid arthritis, hypomagnesemia, and osteoporosis, and suggested potential novel negative associations with commonly used medications.

Incident acute pseudogout and prior bisphosphonate use: Matched case-control study in the UK-Clinical Practice Research Datalink

Oral bisphosphonates are the most commonly used drugs to treat postmenopausal osteoporosis. Acute pseudogout is anecdotally reported to occur following bisphosphonate initiation but empirical data are lacking. We investigated whether treatment with oral bisphosphonates is a risk factor for incident acute pseudogout.A matched case-control study was undertaken using data from the UK-Clinical Practice Research Datalink. Adults who consulted for incident acute pseudogout between 1987 and 2012 were each matched for gender, age at pseudogout diagnosis, and general practice to up to 4 control subjects without pseudogout. The exposure of interest was a prescription for an oral bisphosphonate issued within the 60-day period prior to the date of incident acute pseudogout. Associations between incident acute pseudogout and prior bisphosphonate prescription were examined using conditional logistic regression, adjusting for hyperparathyroidism, osteoarthritis, rheumatoid arthritis, hemochromatosis, hypophosphatasia, and prescriptions for diuretics and oral corticosteroids.Two thousand eleven acute pseudogout cases were compared with 8013 matched controls without acute pseudogout (mean age [standard deviation] 72 years [14]; 52% male). One hundred twenty-three cases (6.1%) had received an oral bisphosphonate prescription in the 60-day exposure period compared with 305 controls (3.8%) (adjusted incidence rate ratio [IRR] 1.33; 95% confidence interval [CI] 1.05-1.69). This association was stronger in females (adjusted IRR 1.49; 95% CI 1.15-1.94) and was nonsignificant in males (0.83; 0.48-1.44).Incident acute pseudogout was associated with prescription of an oral bisphosphonate in the preceding 60 days. Prescribers should be aware of acute pseudogout as a possible side effect of bisphosphonate treatment. Further research is needed to explore the risks conferred by different bisphosphonates and the mechanism underlying this association.

Calcium pyrophosphate deposition disease: a review of epidemiologic findings

PURPOSE OF REVIEW

The purpose of this review is to summarize the recent advances in the epidemiology of calcium pyrophosphate deposition disease (CPPD), and to discuss their implications. This review is particularly timely as several epidemiological studies that enhance the understanding of CPPD have been published recently.

RECENT FINDINGS

This article will review recent findings on the prevalence of chondrocalcinosis; discuss new data on the associations between bone mineral density and chondrocalcinosis; and between diuretic use, chronic kidney disease 5 and 'pseudogout' (now termed acute calcium pyrophosphate crystal arthritis). It will summarize findings from a large dataset which reported that chondrocalcinosis results from a systemic predisposition, and that the association between chondrocalcinosis and polymorphisms in ANKH gene is independent of age and osteoarthritis. It will also review recent data which suggest that the association between chondrocalcinosis and osteoarthritis may be joint specific, and that chondrocalcinosis associates with radiographic attrition in knees with osteoarthritis.

SUMMARY

The studies reviewed suggest that CPPD occurs due to a generalized predisposition, and that it modifies the radiographic phenotype of osteoarthritis. However, further research is required to confirm if CPPD modifies the clinical phenotype of osteoarthritis.

Coexistent Pseudogout and Mycobacterium avium-intracellulare Septic Arthritis in a Patient with HIV and ESRD

Pseudogout is a crystal-induced arthropathy characterized by the deposition of calcium pyrophosphate dihydrate (CPPD) crystals in synovial fluid, menisci, or articular cartilage. Although not very common, this entity can be seen in patients with chronic kidney disease (CKD). Septic arthritis due to Mycobacterium avium-intracellulare (MAI) is a rare entity that can affect immunocompromised patients such as those with acquired immunodeficiency syndrome (AIDS) or those who are on immunosuppressive drugs. Here, we describe a 51-year-old female who presented with fever, right knee pain, swelling, warmth, and decreased range of motion for several days. The initial assessment was consistent with pseudogout, with negative bacterial and fungal cultures. However, due to high white blood cell (WBC) count in the synovial fluid analysis, she was empirically started on intravenous (IV) vancomycin and piperacillin-tazobactam and discharged on IV vancomycin and cefepime, while acid-fast bacilli (AFB) culture was still in process. Seventeen days later, AFB culture grew Mycobacterium avium-intracellulare (MAI), and she was readmitted for relevant management. This case illustrates that septic arthritis due to MAI should be considered in the differential diagnosis of septic arthritis in immunocompromised patients.

Validation of administrative codes for calcium pyrophosphate deposition: a Veterans Administration study

BACKGROUND

Despite high prevalence, progress in calcium pyrophosphate deposition (CPPD) has been limited by poor awareness and absence of validated approaches to study it in large data sets.

OBJECTIVES

We aimed to determine the accuracy of administrative codes for the diagnosis of CPPD as a foundational step for future studies.

METHODS

We identified all patients with an International Classification of Diseases, Ninth Revision, Clinical Modification code for chondrocalcinosis (712.1-712.39) or pseudogout/other disorders of mineral metabolism (275.49), and convenience sample selected a comparison group with gout (274.00-03 or 274.8-9), or rheumatoid arthritis (714.0) from 2009 to 2011 at a Veterans Affairs medical center. Each patient was categorized as having definite, probable, or possible CPPD or absence of CPPD based on the McCarty and Ryan criteria using chart abstracted data including crystal analysis, radiographs, and arthritis history.

RESULTS

Two hundred forty-nine patients met the clinical gold standard criteria for CPPD based on medical records, whereas 48 patients met definite criteria, 183 probable, and 18 met possible criteria. The accuracy of administrative claims with a code of 712 or 275.49 for definite or probable CPPD was as follows: 98% sensitivity (95% confidence interval, 96%-99%), 78% specificity (74%-83%), 91% positive predictive value, and 94% negative predictive value.

CONCLUSIONS

At this center, single administrative code 275.49 or 712 accurately identifies patients with CPPD with a positive predictive value of 91%. These findings suggest that administrative codes can have strong clinical accuracy and merit further validation to allow adoption in future epidemiologic studies of CPPD.

[Renal diseases in rheumatology]

Renal involvement and renal function disorders are commonplace in patients with rheumatic diseases and are often decisive for the prognosis. Typical nephrological complications in rheumatology are renal manifestations or delayed sequelae of the underlying disease in addition to drug-induced renal failure, e.g. by nonsteroidal anti-inflammatory drugs (NSAIDs). The differentiation from other common causes of disturbed renal function (e.g. diabetes and hypertension) is important and often difficult in individual cases. Renal involvement can be clinically manifested in many different ways. The spectrum ranges from slight functional disorders with, for example discrete erythrocyturia/proteinuria and normal renal function up to rapidly progressive renal failure. The probability of renal damage also varies greatly between different underlying diseases. For example, renal involvement in rheumatoid arthritis is a rarity but in contrast relatively normal in systemic lupus erythematosus. In the course of the differential diagnostics urine sediment, protein values and sonography are still the most important factors and the indications for kidney biopsy should be generously applied. Early initiation of immunosuppression can substantially improve the renal prognosis of inflammatory systemic diseases.

Epidemiology of calcium pyrophosphate crystal arthritis and basic calcium phosphate crystal arthropathy

Calcium pyrophosphate crystal deposition (CPPD) is common and mainly associates with increasing age and osteoarthritis (OA). Recent studies suggest that CPPD occurs as the result of a generalized articular predisposition and may also associate with low cortical bone mineral density. The epidemiology of basic calcium phosphate (BCP) crystal deposition is poorly understood. Although periarticular BCP crystal deposits occurs at all ages and in both sexes, intra-articular BCP crystal deposition tends to associate with increasing age and OA. Calcium pyrophosphate and BCP crystals frequently coexist in joints with OA.

Imaging joints for calcium pyrophosphate crystal deposition: a knock to the knees

With advanced age, articular calcium pyrophosphate crystal deposition (CPPD) is common. Defining who has CPPD is of growing importance, given increases in longevity in many countries and the frequent association of chondrocalcinosis with osteoarthritis. Chondrocalcinosis detected by plain radiography serves as a major screening tool, but how many and which sites to screen have not been adequately defined in the past. The work of Abhishek and colleagues in the previous issue of Arthritis Research and Therapy sheds new light on the incomplete information from knee radiographs, and helps position us to learn more about the epidemiology, pathophysiology, diagnosis, and clinical impact of CPPD.