Daniel J McCarty, MD: A Giant of Rheumatology.

There is no doubt that Dr Daniel J McCarty warrants inclusion among the giants of rheumatology. He has made major contributions to both clinical and scientific knowledge in our field, and his impact has been long-lasting and paradigm shifting. He is perhaps best known for his pioneering work in crystal arthritis, but as an astute clinician, he is also responsible for describing several other novel rheumatic conditions and developing innovative treatment protocols.

Identification of Common Pathogenic Pathways Involved in Hemochromatosis Arthritis and Calcium Pyrophosphate Deposition Disease: a Review.

OBJECTIVES: Arthritis is a common clinical manifestation of hereditary hemochromatosis (HH), and HH is one of a handful of conditions linked to calcium pyrophosphate deposition (CPPD) in joints. The connection between these two types of arthritis has not yet been fully elucidated. In light of new pathogenic pathways recently implicated in CPPD involving bone, we reviewed the literature on the etiology of hemochromatosis arthropathy (HHA) seeking shared pathogenic mechanisms. RESULTS: Clinical observations reinforce striking similarities between HHA and CPPD even in the absence of CPP crystals. They share a similar joint distribution, low grade synovial inflammation, and generalized bone loss. Excess iron damages chondrocytes and bone cells in vitro. While direct effects of iron on cartilage are not consistently seen in animal models of HH, there is decreased osteoblast alkaline phosphatase activity, and increased osteoclastogenesis. These abnormalities are also seen in CPPD. Joint repair processes may also be impaired in both CPPD and HHA. CONCLUSIONS: Possible shared pathogenic pathways relate more to bone and abnormal damage/repair mechanisms than direct damage to articular cartilage. While additional work is necessary to fully understand the pathogenesis of arthritis in HH and to firmly establish causal links with CPPD, this review provides some plausible hypotheses explaining the overlap of these two forms of arthritis.

Pathogenesis of calcium pyrophosphate deposition disease.

Calcium pyrophosphate deposition disease is defined by the presence of calcium pyrophosphate (CPP) crystals in articular cartilage and is the fourth most common type of arthritis in adults. Despite its high prevalence, the etiology of CPPD disease remains unclear and no specific therapies currently exist. It has been known for several decades that abnormalities of cartilage pyrophosphate metabolism are common in patients with CPPD disease, and this classic work will be reviewed here. Recent studies of rare familial forms of CPPD disease have provided additional novel information about its pathophysiology. This work suggests that CPPD disease occurs through at least two unique and potentially intertwined biomolecular pathways. We are hopeful that a detailed understanding of the components and regulation of these pathways will lead to improved therapies for this common disease.

Calcium pyrophosphate crystal size and characteristics.

OBJECTIVE: To describe the characteristics of calcium pyrophosphate (CPP) crystal size and morphology under compensated polarized light microscopy (CPLM). Secondarily, to describe CPP crystals seen only with digital enhancement of CPLM images, confirmed with advanced imaging techniques. METHODS: Clinical lab-identified CPP-positive synovial fluid samples were collected from 16 joint aspirates. Four raters used a standardized protocol to describe crystal shape, birefringence strength and color. A crystal expert confirmed CPLM-visualized crystal identification. For crystal measurement, a high-pass linear light filter was used to enhance resolution and line discrimination of digital images. This process identified additional enhanced crystals not seen by raters under CPLM. Single-shot computational polarized light microscopy (SCPLM) provided further confirmation of the enhanced crystals' presence. RESULTS: Of 932 suspected crystals identified by CPLM, 569 met our inclusion criteria, and 293 (51%) were confirmed as CPP crystals. Of 175 unique confirmed crystals, 118 (67%) were rods (median area 3.6 µm2 [range, 1.0-22.9 µm2]), and 57 (33%) were rhomboids (median area 4.8 µm2 [range, 0.9-16.7 µm2]). Crystals visualized only after digital image enhancement were smaller and less birefringent than CPLM-identified crystals. CONCLUSIONS: CPP crystals that are smaller and weakly birefringent are more difficult to identify. There is likely a population of smaller, less birefringent CPP crystals that routinely goes undetected by CPLM. Describing the characteristics of poorly visible crystals may be of use for future development of novel crystal identification methods.

Towards development of core domain sets for short term and long term studies of calcium pyrophosphate crystal deposition (CPPD) disease: A framework paper by the OMERACT CPPD working group.

INTRODUCTION: Although calcium pyrophosphate deposition (CPPD) is common, there are no published outcome domains or validated measurement instruments for CPPD studies. In this paper, we describe the framework for development of the Outcome Measures in Rheumatology (OMERACT) CPPD Core Domain Sets. METHODS: The OMERACT CPPD working group performed a scoping literature review and qualitative interview study. Generated outcomes were presented at the 2020 OMERACT CPPD virtual Special Interest Group (SIG) meeting with discussion focused on whether different core domain sets should be developed for different calcium pyrophosphate deposition (CPPD) clinical presentations and how the future CPPD Core Domain Set may overlap with already established osteoarthritis (OA) domains. These discussions informed development of a future work plan for development of the OMERACT CPPD Core Domain Sets. FINDINGS: Domains identified from a scoping review of 112 studies and a qualitative interview study of 36 people (28 patients with CPPD, 7 health care professionals, one stakeholder) were mapped to core areas of OMERACT Filter 2.1. The majority of SIG participants agreed there was need to develop separate core domain sets for "short term" and "long term" studies of CPPD. Although CPPD + OA is common and core domain sets for OA have been established, participants agreed that existing OA core domain sets should not influence the development of OMERACT core domain sets for CPPD. Prioritization exercises (using Delphi methodology) will consider 40 potential domains for short term studies of CPPD and 47 potential domains for long term studies of CPPD. CONCLUSION: Separate OMERACT CPPD Core Domain Sets will be developed for "short term" studies for an individual flare of acute CPP crystal arthritis and for "long term" studies that may include participants with any clinical presentation of CPPD (acute CPP crystal arthritis, chronic CPP crystal inflammatory arthritis, and/or CPPD + OA).

The value of anti-CarP and anti-PAD4 as markers of rheumatoid arthritis in ACPA/RF negative rheumatoid arthritis patients.

BACKGROUND: Anti-citrullinated protein antibodies (ACPAs) and rheumatoid factor (RF) are key factors in the American College of Rheumatology/European League Against Rheumatism rheumatoid arthritis (RA) classification criteria markers. However, about 30% of patients diagnosed with RA are seronegative, rationalizing the need for new serologic markers for RA. Antibodies against carbamylated proteins (anti-CarP) and against peptidyl-arginine deiminase type 4 (anti-PAD4) have been postulated to be useful RA markers. The purpose of this study is to evaluate the value of anti-CarP and anti-PAD4 in a well-characterized population of RA patients and healthy controls (HCs). METHODS: A total of 122 RA patients and 30 HCs were enrolled in the study. Serum levels of ACPA, anti-PAD4, anti-CarP and RF were determined by enzyme-linked immunosorbent immunoassays (ELISAs). Synthetic carbamylated peptides were used in the ELISA assay to determine the protein targets of the anti-CarP antibodies. RESULTS: Rates of ACPA, RF, anti-PAD4 and anti-CarP positivity were 85.2%, 67.2%, 55.7% and 46.7% in RA, and 0%, 0%, 6.7% and 6.7% in HC respectively. In the RA population, 25.4% of patients had all four types of antibodies positive, while 6.6% had no antibodies. There was a significant correlation between anti-PAD4 and ACPAs (r s = 0.39), RF and ACPAs, (r s = 0.3) and RF and anti-CarP, (r s = 0.3). There was no correlation between ACPAs and anti-CarP. Anti-CarP positivity was noted in 49 (47.1%) and 45 (54.9%) of ACPAs and RF positive patients respectively. In addition, five anti-CarP+ patients did not have ACPA nor RF. CONCLUSION: Anti-CarP but not anti-PAD4 may be a useful biomarker in identifying ACPA/RF negative RA patients. This antibody may identify an additional RA population who may benefit from early implementation of aggressive therapy.

Effects of the TNFRSF11B Mutation Associated With Calcium Pyrophosphate Deposition Disease in Osteoclastogenesis in a Murine Model.

OBJECTIVE: The gene TNFRSF11B encodes for osteoprotegerin (OPG) and was recently identified as the CCAL1 locus associated with familial calcium pyrophosphate deposition disease (CPDD). While the CCAL1 OPG mutation (OPG-XL) was originally believed to be a gain-of-function mutation, loss of OPG activity causes arthritis-associated osteolysis in mice, which is likely related to excess subchondral osteoclast formation and/or activity. The purpose of the present study was to further explore the effect of OPG-XL in osteoclastogenesis. METHODS: The effects of recombinant OPG-XL and wild-type (WT) OPG were determined in monoculture and coculture models of RANKL-induced osteoclastogenesis. The effects of OPG-XL on osteoclast survival as well as on TRAIL-induced apoptosis were determined using standard in vitro assays and compared to WT OPG. The ability of OPG-XL and WT OPG to bind to osteoblasts was measured with enzyme-linked immunosorbent assay and flow cytometry using the osteoblastic MC3T3-E1 cell line. RESULTS: OPG-XL was less effective than WT OPG at blocking RANKL-induced osteoclastogenesis in monoculture and coculture models. Osteoclast survival and inhibition of TRAIL-induced apoptosis were similar in the presence of OPG-XL and WT OPG. Compared to WT OPG, considerably less OPG-XL bound to cells. CONCLUSION: These findings indicate that OPG-XL is a loss-of-function mutation as it relates to RANKL-mediated osteoclastogenesis, and thus may permit increased osteoclast numbers and heightened bone turnover. Further studies are necessary to demonstrate how this mutation contributes to arthritis in individuals carrying this mutation.

Management of calcium pyrophosphate crystal deposition disease: A systematic review.

OBJECTIVE: Calcium pyrophosphate crystal deposition disease (CPPD) is a common cause of acute and chronic arthritis, especially in the elderly population. There is a paucity of data regarding the management of CPPD disease, which is currently based on expert opinion and evidence derived from the treatment of gout. We conducted a systematic literature review in order to identify the available treatment options for CPPD, and describe their efficacy and safety. MATERIAL AND METHODS: Online databases were searched from inception to May of 2020 using the search terms: (CPPD [Title/Abstract] OR CPDD [Title/Abstract] OR calcium pyrophosphate [Title/Abstract] OR chondrocalcinosis [Title/Abstract]) AND (treatment [Title/Abstract] OR management [Title/Abstract] OR therapy [Title/Abstract]). Articles evaluating the use of specific treatment agents for CPPD were eligible for inclusion. Case reports were excluded. RESULTS: A total of 22 eligible studies and 403 unique patients were selected. We identified only 3 randomized, double-blind, controlled trials (RCTs) evaluating the use of methotrexate, hydroxychloroquine, and magnesium carbonate in CPPD, and these therapeutic options, with the exception of methotrexate, have shown efficacy and reduction of pain intensity. Further, 10 case series and 9 cohort studies were included. Intramuscular and intra-articular glucocorticoids, ACTH, as well as the biologic agents anakinra and tocilizumab appear to be efficacious in CPPD. Intra-articular injections of glycosaminoglycan polysulphate, hyaluronic acid and yttrium, as well as synovial membrane destruction by laser irradiation were associated with symptomatic improvement. Due to significant study heterogenicity, direct comparison between studies was not possible. CONCLUSION: There are a limited number of studies evaluating the treatment of CPPD. High quality evidence is rather limited, while commonly administered agents such as NSAIDs, colchicine and corticosteroids have not been evaluated by RCTs. The need for high quality evidence supporting specific treatment modalities is urgent for this common yet neglected form of arthritis.

Hypermethylation of the miR-155 gene in the whole blood and decreased plasma level of miR-155 in rheumatoid arthritis.

OBJECTIVES: miR-155 plays a critical role in the inflammatory process and in diseases such as rheumatoid arthritis (RA). miR155 gene expression is regulated by its gene promoter region CpG island methylation. Previous studies have shown inconsistent changes in circulating levels of mir-155 in RA patients. The aims of our study were to evaluate miR-155 levels in plasma, to investigate its gene methylation level, and to correlate these levels with RA disease activity. METHODS: One hundred and twenty-five patients with RA, and 30 age and sex-matched healthy controls (HC) were enrolled. Whole blood and plasma samples were collected and stored at -80°C until analysis. DAS28 score at the time of the blood draw was used to assess RA disease activity. The methylation status of miR-155 host gene was determined in whole blood by quantitative real-time methylation-specific PCR (qPCR). miR-155 expression levels were evaluated by quantitative reverse transcription PCR. RESULTS: We found significantly lower circulating miR155 levels in RA patients compared to HC. Interestingly, the miR-155 gene methylation level was significantly higher in RA patients than in HC. miR-155 levels did not correlate with ACPA or RF positivity or disease activity. CONCLUSIONS: We show here higher miR-155 methylation in whole blood and lower plasma miR155 expression in RA patients in comparison to HC. The evaluation of miR-155 host gene methylation status or miR155 plasma level might be a potentially useful marker in RA determination.

Review: Unmet Needs and the Path Forward in Joint Disease Associated With Calcium Pyrophosphate Crystal Deposition.

Calcium pyrophosphate (CPP) crystal deposition (CPPD) is prevalent and can be associated with synovitis and joint damage. The population of elderly persons predominantly affected by CPPD is growing rapidly. Since shortfalls exist in many aspects of CPPD, we conducted an anonymous survey of CPPD unmet needs, prioritized by experts from the Gout, Hyperuricemia and Crystal-Associated Disease Network. We provide our perspectives on the survey results, and we propose several CPPD basic and clinical translational research pathways. Chondrocyte and cartilage culture systems for generating CPP crystals in vitro and transgenic small animal CPPD models are needed to better define CPPD mechanism paradigms and help guide new therapies. CPPD recognition, clinical research, and care would be improved by international consensus on CPPD nomenclature and disease phenotype classification, better exploitation of advanced imaging, and pragmatic new point-of-care crystal analytic approaches for detecting CPP crystals. Clinical impacts of CPP crystals in osteoarthritis and in asymptomatic joints in elderly persons remain major unanswered questions that are rendered more difficult by current inability to therapeutically limit or dissolve the crystal deposits and assess the consequent clinical outcome. Going forward, CPPD clinical research studies should define clinical settings in which articular CPPD does substantial harm and should include analyses of diverse clinical phenotypes and populations. Clinical trials should identify the best therapeutic targets to limit CPP crystal deposition and associated inflammation and should include assessment of intraarticular agents. Our perspective is that such advances in basic and clinical science in CPPD are now within reach and can lead to better treatments for this disorder.

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.

Basic calcium phosphate crystal-associated musculoskeletal syndromes: an update.

PURPOSE OF REVIEW: Basic calcium phosphate (BCP) crystals are associated with two important musculoskeletal syndromes. Deposition of BCP crystals in tendons, bursae, and other soft tissues around joints causes calcific periarthritis, whereas intra-articular BCP crystals contribute to osteoarthritis and cause the highly destructive arthritis known as Milwaukee Shoulder Syndrome. The epidemiology and natural history of these syndromes are poorly understood, and because the pathogenesis remains unclear, few targeted therapies are available. I will review new developments in this field. RECENT FINDINGS: I will discuss a case collection of calcific periarthritis of the hip, and evidence-based management strategies for shoulder calcific periarthritis that might be applied to calcific periarthritis at other locations. I will summarize several recent articles addressing mechanisms of crystal formation and identifying pathways through which BCP crystals produce tissue damage and explore some newly identified risk factors for pathologic mineralization. SUMMARY: We are making slow, but steady progress in understanding the clinical presentation of calcific periarthritis in sites other than the shoulder. A growing appreciation of the mechanisms through which BCP crystals mediate tissue damage should lead to the development of novel management strategies for these common musculoskeletal syndromes.

Erosive osteoarthritis: A systematic analysis of definitions used in the literature.

BACKGROUND: Erosive osteoarthritis (EOA) is a commonly invoked diagnosis representing an important variant of hand osteoarthritis (OA). There is increasing literature on the prevalence, risk factors, etiology, and management of EOA. METHODS: We systematically reviewed the literature to assess variability in the diagnostic definitions used to define EOA in these studies. RESULTS: We reviewed 336 articles and found 62 articles citing diagnostic definitions for EOA. Radiographic appearance was the most commonly used criterion, but there was little agreement on the details or extent of the radiographic changes. Overall, 56 of the 62 studies included clinical features in the diagnostic definitions, yet these features varied considerably. Exclusion criteria were mentioned in 43 of the studies. CONCLUSION: Based on the widely disparate definitions of EOA, we urge caution in interpretation of this literature, and propose that further understanding of EOA will require consensus on its definition.

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.

Pauci-Immune Crescentic Glomerulonephritis in Connective Tissue Disease.

Pauci-immune crescentic glomerulonephritis is commonly seen in ANCA-associated vasculitis but it is rarely seen during the course of other connective tissue diseases like lupus or Sjogren's syndrome or MCTD. We report 3 cases of pauci-immune crescentic glomerulonephritis in patients with connective tissue disease other than vasculitis. We reviewed literature and made summary of previously reported cases of this rare entity. Clinical and laboratory features of these patients varied widely, but most of patients have met criteria for lupus. In this small population of patients there is no correlation with ANCAs. Most of the patients were treated with aggressive immunosuppression and did well if they were treated early in the course of their disease. One of our patients required renal transplant, but she presented late in the course of her disease, as evidenced by chronicity on her renal biopsy. Whether these patients are overlap of vasculitis and other connective tissue diseases or to be considered as a separate entity is yet to be described. Clinicians must be aware of these presentations because initial presentation can be severe.

The Role of ANK in Calcium Pyrophosphate Deposition Disease.

The protein product of the progressive ankylosis gene, known as ANK, is a 492-amino acid multi-pass transmembrane protein. This protein is critical for the regulation of pyrophosphate, and gain of function ANK mutations is associated with calcium pyrophosphate deposition disease. Much about the structure, function, and regulation of ANK remain unstudied. This review of the current literature examines recent contributions to our understanding of ANK. We focus on new work on the function, binding partners, and regulators of ANK. A more complete understanding of this important protein may help to identify future therapeutic targets for the treatment of calcium pyrophosphate deposition disease.

Articular cartilage vesicles and calcium crystal deposition diseases.

PURPOSE OF REVIEW: Articular cartilage vesicles (ACVs) are small extracellular vesicles that serve as foci of pathologic calcium crystal deposition in articular cartilage matrix. In this review, I have summarized the role of ACVs in calcium crystal formation and discuss recent findings that impact our understanding of the content, behavior, and origin of ACVs in healthy and diseased joints. The burgeoning interest in extracellular vesicles in other fields renders this a timely and relevant topic. RECENT FINDINGS: I have highlighted recent studies demonstrating that some ACVs originate in the autophagic pathway in healthy articular chondrocytes. I have reviewed accumulating evidence that nonmineralizing functions of ACVs contribute to osteoarthritis. I have also discussed new work supporting a role for extracellular vesicles in interleukin-1ß-induced mineralization and in mediating the catabolic effects of synovial inflammation in osteoarthritis. SUMMARY: We are making slow and steady progress in understanding the origin and function of ACVs and other relevant extracellular vesicles in arthritis. Further work in this interesting area is warranted.