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Summary: Nuclear interferon‐inducible protein 16 (IFI16) and anti‐IFI16 antibodies have been detected in subjects with several rheumatic diseases, often correlating with disease severity, and in this study we investigated their prevalence and clinical associations in psoriatic arthritis (PsA) compared to psoriasis (Pso). We tested sera and synovial fluids of patients with PsA for IFI16 protein levels by capture enzyme‐linked immunosorbent assay (ELISA) and for anti‐IFI16 immunoglobulin (Ig)G and IgA by ELISA, protein radio‐immunoprecipitation and immunoprecipitation‐Western blot of IgG. Sera from patients with Pso and healthy subjects were used as controls, and in a subgroup of patients with PsA we also studied sera after treatment with etanercept. IFI16 was detectable in the sera of 66% of patients with Pso, 46% with PsA and 19% of controls. Among PsA cases, 51% of IFI16‐positive cases had elevated levels of C‐reactive protein (CRP) compared to 31% of patients with undetectable IFI16. Anti‐IFI16 of both IgG and IgA isoforms were detected with significantly higher frequency in PsA and Pso compared to healthy controls, with higher IgG titres in patients with elevated C‐reactive protein (CRP) (P = 0·015). Immunoprecipitation confirmed the presence of anti‐IFI16 IgG antibodies and these preferentially recognized epitopes outside the N‐terminus of the protein. Lastly, IFI16 was detected in one of seven and anti‐IFI16 in three of seven synovial fluids from patients with PsA. Therefore, IFI16 and anti‐IFI16 are detectable in serum and synovial fluid of PsA patients, especially in cases of elevated CRP. [ABSTRACT FROM AUTHOR]

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., Competing Interests: Declaration of interests TP received consulting fees from Avalo Therapeutics. GF has received a research grant from Lilly. All other authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license. Published by Elsevier Ltd.. All rights reserved.)

Purpose of the Review: Although calcium pyrophosphate deposition (CPPD) has been known since the 1960s, our understanding of its pathogenesis remains rudimentary. This review aims to illustrate the known mechanisms underlying calcium pyrophosphate (CPP) crystal formation and deposition and explore future directions in research. By examining various perspectives, from basic research to clinical and imaging assessments, as well as new emerging methodologies, we can establish a starting point for a deeper understanding of CPPD pathogenesis., Recent Findings: Recent years have seen significant advances in CPPD research, particularly in the clinical field with the development of the 2023 ACR/EULAR classification criteria for CPPD disease, and in imaging with the introduction of the OMERACT ultrasonographic definitions and scoring system. However, progress in basic research has been slower. New laboratory approaches, such as Raman spectroscopy and omics sciences, offer promising insights that may help piece together the puzzle of CPPD. CPPD is a common yet understudied condition. As the population ages and CPPD becomes more prevalent, there is an urgent need to better understand the disease and the mechanisms involved in crystal formation and deposition, in order to improve diagnosis and therapeutic approaches., (© 2024. The Author(s).)

Competing Interests: Competing interests: None declared.

Background: The purpose of the authors' narrative review was to outline the current literature regarding the use of ultrasound in main rheumatic disorders and summarize the updates, specifically about rheumatoid arthritis, psoriatic arthritis, and crystal-induced arthropathies., Methods: The authors searched on PubMed for articles discussing the major updates regarding the role of ultrasound in the previously mentioned rheumatic conditions., Results: The authors have provided the updated definitions, new criteria, and diagnostic scores., Conclusions: In rheumatology's dynamic landscape, this review provides valuable insights for researchers and clinicians on ultrasound's role in improving patient care and outcomes in rheumatic diseases., Competing Interests: Disclosure L.M. Sconfienza has financial relationship with Esaote SpA and Samsung Medison, all unrelated to the present paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Objective: The study objective was to examine the disease, demographic, and imaging features associated with different inflammatory phenotypes of calcium pyrophosphate deposition (CPPD) disease, ie, recurrent acute calcium pyrophosphate (CPP) crystal arthritis, chronic CPP crystal inflammatory arthritis, and crowned dens syndrome (CDS)., Methods: Data from an international cohort (assembled from 25 sites in 7 countries for the development and validation of the 2023 CPPD classification criteria from the American College of Rheumatology/EULAR) that met the criteria were included. Three cross-sectional studies were conducted to determine the phenotypic characteristics of recurrent acute CPP crystal arthritis, chronic CPP crystal inflammatory arthritis, and CDS. Multivariable logistic regression analysis was used to calculate adjusted odds ratio (aOR) and 95% confidence interval (CI) to examine the association between potential risk factors and the inflammatory phenotype., Results: Among the 618 people included (56% female; mean age [standard deviation] 74.0 [11.9] years), 602 (97.4%) had experienced acute CPP crystal arthritis, 332 (53.7%) had recurrent acute arthritis, 158 (25.6%) had persistent inflammatory arthritis, and 45 (7.3%) had had CDS. Recurrent acute CPP crystal arthritis associated with longer disease duration (aOR 2.88 [95% CI 2.00-4.14]). Chronic CPP crystal inflammatory arthritis was associated with acute wrist arthritis (aOR 2.92 [95% CI 1.81-4.73]), metacarpophalangeal joint osteoarthritis (aOR 1.87 [95% CI 1.17-2.97]), and scapho-trapezo-trapezoid (STT) joint osteoarthritis (aOR 1.83 [95% CI 1.15-2.91]), and it was negatively associated with either metabolic or familial risk for CPPD (aOR 0.60 [95% CI 0.37-0.96]). CDS was associated with male sex (aOR 2.35 [95% CI 1.21-4.59]), STT joint osteoarthritis (aOR 2.71 [95% CI 1.22-6.05]), and more joints affected with chondrocalcinosis (aOR 1.46 [95% CI 1.15-1.85])., Conclusion: CPPD disease encompasses acute and chronic inflammatory phenotypes, each with specific clinical and imaging features that need to be considered in the diagnostic workup., (© 2024 The Author(s). Arthritis & Rheumatology published by Wiley Periodicals LLC on behalf of American College of Rheumatology.)

Objective: To develop the optimal US scanning protocol for the diagnosis of calcium pyrophosphate crystal deposition (CPPD) disease., Methods: In this cross-sectional study, consecutive patients with a crystal-proven diagnosis of CPPD disease, and age-, sex-matched disease controls with a negative synovial fluid analysis were prospectively enrolled in two Italian Institutions. Four rheumatologists, blinded to patients' clinical details, performed US examinations using a standardized scanning protocol including 20 joints (shoulders, elbows, wrists, metacarpophalangeal joints from second to fifth fingers, hips, knees, ankles). CPPD was identified as presence/absence, according to the OMERACT definitions. Reduced US scanning protocols were developed by selecting the most informative joints to be imaged by US using the LASSO technique. Patients were randomly divided into training and validation sets. Their diagnostic accuracy was tested comparing the area under the receiver operating characteristic curves., Results: The number of participants enrolled was 204: 102 with CPPD disease and 102 disease controls [age, mean (s.d.): 71.3 (12.0) vs 71.1 (13.5) years; female: 62.8% vs 57.8%]. The median number of joints with US evidence of CPPD was 5 [interquartile range (IQR): 4-7] and 0 (IQR: 0-1) in patients with CPPD disease and controls, respectively (P < 0.01). The detection of CPPD in ≥2 joints using a reduced scanning protocol (bilateral assessment of knees, wrists and hips) showed a sensitivity of 96.7% (95% CI: 82.8, 99.9) and a specificity of 100 (95% CI: 88.8, 100.0) for the diagnosis of CPPD disease and had good feasibility [mean (s.d.): 12.5 (5.3) min]., Conclusion: Bilateral US assessment of knees, wrists and hips had excellent accuracy and good feasibility for the diagnosis of CPPD disease., (© The Author(s) 2023. Published by Oxford University Press on behalf of the British Society for Rheumatology.)

Purpose of Review: Fibromyalgia Syndrome (FMS) is a complex chronic pain condition characterized by widespread musculoskeletal pain and numerous other debilitating symptoms. The purpose of this review is to provide a comprehensive overview, based on everyday clinical practice, of the drugs presently employed in the treatment of FMS., Recent Findings: The treatment of FMS is based on a multimodal approach, with pharmacologic treatment being an essential pillar. The drugs used include tricyclic antidepressants, serotonin and noradrenaline reuptake inhibitors, other antidepressants, anticonvulsants, myorelaxants, and analgesics. The effectiveness of these medications varies, and the choice of drug often depends on the specific symptoms presented by the patient. Many drugs tend to either address only some domains of the complex FMS symptomatology or have a limited effect on pain. Each treatment option comes with potential side effects and risks that necessitate careful consideration. It may be beneficial to divide patients into clinical subpopulations, such as FMS with comorbid depression, for more effective treatment. Despite the complexities and challenges, the pharmacological treatment remains a crucial part for the management of FMS. This review aims to guide clinicians in prescribing pharmacological treatment to individuals with FMS., (© 2024. The Author(s).)

Introduction: Osteoarthritis (OA) and calcium pyrophosphate deposition (CPPD) often co-exist, this resulting in a clinical condition characterized by amplified inflammation and more severe and faster cartilage degeneration compared to OA alone. Our study aims to explore the efficacy of a therapeutic approach that addresses both conditions, using a combination of a high molecular weight hyaluronic acid (HMWHA) and collagen tripeptide (CTP). Additionally, safety profile and baseline characteristic predictive value were evaluated., Methods: We conducted a retrospective study on patients diagnosed with symptomatic knee OA (KOA) and CPPD treated by ultrasound (US) guided intraarticular injections of HMWHA-CT in the outpatient clinics of the Interdisciplinary Pain Medicine Unit at Santa Maria Maddalena Hospital, Occhiobello, Italy and in the Rheumatology Unit of the Emergency County Hospital Craiova, Romania (ECH Craiova). All the patients underwent clinical and US evaluation at baseline, 1, 3, and 6 months. From clinical point of view, Numeric Rating Scale (NRS) pain and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) were recorded. US data included detection of synovitis, cartilage damage, osteophytes, and CPPD deposits. Clinical efficacy was defined with NRS and WOMAC variations in respect to baseline and using the minimal clinically important difference values: an improvement of 2 point for NRS pain and 10 for the total score for WOMAC., Results: Twenty-nine patients (34 knees) were injected and evaluated. Overall pain levels, as measured by NRS, demonstrated a consistent decrease in patients across all follow-up intervals, with the most substantial improvement at the 6-month compared to baseline measurements. A significative proportion of patients achieved the minimum clinically detectable improvement, specifically 79% for NRS and 83% for WOMAC (19 and 20 patients, respectively)., Conclusion: Our data showed a significant efficacy of ultrasound guided HMWHA-CT, in patients with KOA and CPPD, thus making it reasonable to consider that the combination of HMWHA and CTP can provide a strong anti-inflammatory effect., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Porta, Filippucci, Cipolletta, La Grua, Barni, Sirotti and Vreju.)

Introduction: This review delves into Fibromyalgia Syndrome (FMS), a chronic pain condition demanding thorough understanding for precise diagnosis and treatment. Yet, a definitive pharmacological solution for FMS remains elusive., Areas Covered: In this article, we systematically analyze various pharmacotherapeutic prospects for FMS treatment, organized into sections based on the stage of drug development and approval. We begin with an overview of FDA-approved drugs, discussing their efficacy in FMS treatment. Next, we delve into other medications currently used for FMS but still undergoing further study, including opioids and muscle relaxants. Further, we evaluate the evidence behind medications that are currently under study, such as cannabinoids and naltrexone. Lastly, we explore new drugs that are in phase II trials. Our research involved a thorough search on PUBMED, Google Scholar, and clinicaltrials.gov. We also discuss the action mechanisms of these drugs and their potential use in specific patient groups., Expert Opinion: A focus on symptom-driven, combination therapy is crucial in managing FMS. There is also a need for ongoing research into drugs that target neuroinflammation, immunomodulation, and the endocannabinoid system. Bridging the gap between benchside research and clinical application is challenging, but it holds potential for more targeted and effective treatment strategies.

Purpose of Review: In 1977, McCarty astutely observed, 'The variety of names suggested for the condition associated with deposits of calcium pyrophosphate dihydrate crystals is exceeded only by the variations of its clinical presentation'. Fast forward to 2024, a standardized nomenclature for calcium pyrophosphate deposition (CPPD) is still lacking. This review aims to delineate the challenges in characterizing CPPD through nomenclature and imaging., Recent Findings: Despite the effort of nomenclature standardization in 2011 by the EULAR, confusion persists in the literature and clinical practice, with pseudo-forms and obscure abbreviations. The Gout, Hyperuricemia and Crystal-Associated Disease Network (G-CAN) has launched a project to redefine CPPD nomenclature and formulate a user-friendly language for effective communication with patients and other stakeholders. Additionally, recent advancements in imaging, have shed light on various aspects of the disorder., Summary: Almost 60 years from the first description of a clinical manifestation related to calcium pyrophosphate crystals, a common language describing the disorder is still lacking. A redefined CPPD nomenclature, together with lay-friendly terminology, would significantly contribute to the uniformity of CPPD research, enhance public understanding and awareness and improve doctor-patient communication and therefore disease outcomes. Imaging can provide deep insights into CPPD elements, promoting comprehension of this disorder., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Pain is a significant issue in rheumatoid arthritis (RA) and psoriatic arthritis (PSA) and can have a negative impact on patients' quality of life. Despite optimal control of inflammatory disease, residual chronic pain remains a major unmet medical need in RA. Pain in RA can be secondary to inflammation but can also generate neuroendocrine responses that initiate neurogenic inflammation and enhance cytokine release, leading to persistent hyperalgesia. In addition to well-known cytokines such as TNFα and IL-6, other cytokines and the JAK-STAT pathway play a role in pain modulation and inflammation. The development of chronic pain in RA involves processes beyond inflammation or structural damage. Residual pain is often observed in patients even after achieving remission or low disease activity, suggesting the involvement of non-inflammatory and central sensitization mechanisms. Moreover, fibromyalgia syndrome (FMS) is prevalent in RA patients and may contribute to persistent pain. Factors such as depression, sleep disturbance, and pro-inflammatory cytokines may contribute to the development of fibromyalgia in RA. It is essential to identify and diagnose concomitant FMS in RA patients to better manage their symptoms. Further research is needed to unravel the complexities of pain in RA. Finally, recent studies have shown that JAK inhibitors effectively reduce residual pain in RA patients, suggesting pain-reducing effects independent of their anti-inflammatory properties., Competing Interests: Declaration of competing interest None, (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Objectives: Very little is known on the efficacy and safety of drugs for the management of chronic calcium pyrophosphate (CPP) crystal inflammatory arthritis. The objectives of this work were to describe the drugs used in the management of chronic CPP crystal inflammatory arthritis in expert European centres, and to examine treatment retention., Methods: This was a retrospective cohort study. Charts from patients with a diagnosis of persistent inflammatory and/or recurrent acute CPP crystal arthritis were reviewed in seven European centres. Baseline characteristics were collected, and visits at months 3, 6, 12 and 24 included an assessment of treatment response and safety., Results: One hundred and ninety-four treatments were initiated in 129 patients. Colchicine (used first-line in n = 73/86), methotrexate (used first-line in n = 14/36), anakinra (n = 27) and tocilizumab (n = 25) were the most prescribed treatments, while long-term corticosteroids, hydroxychloroquine, canakinumab and sarilumab were used occasionally. The 24-month on-drug retention was higher for tocilizumab (40%) than anakinra (18.5%) (P < 0.05), while the difference between colchicine (29.1%) and methotrexate (44.4%) was not statistically significant (P = 0.10). Adverse events led to 14.1% of colchicine discontinuations (100% of diarrhoea), 4.3% for methotrexate, 31.8% for anakinra and 20% for tocilizumab; all other discontinuations were related to insufficient response or losses to follow-up. Efficacy outcomes did not differ significantly between treatments throughout follow-up., Conclusion: Daily colchicine is the first-line therapy used in chronic CPP crystal inflammatory arthritis, which is considered efficient in a third to half of cases. Second-line treatments include methotrexate and tocilizumab, which have higher retention than anakinra., (© The Author(s) 2023. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

New evidence from 2022 slightly changed some perspectives for rheumatoid arthritis (RA) management. Real-world data on the efficacy and safety of disease-modifying anti-rheumatic drugs strengthened the importance of tailoring treatment decisions based on patient characteristics. Moreover, the research of response biomarkers to therapy underlined the need for precision medicine and remote care applications showed an innovative outlook that supports a patient-centred approach. New developments in vaccinations led to the release of updated guidelines and to a consistent improvement in the prevention of vaccine-preventable infections. New literature data also reconsidered drug management in RA-associated interstitial lung disease and pregnancy. In this paper, the reviewers aim to present the most relevant studies published during the last year in the field of RA management.

Objective: Calcium pyrophosphate deposition (CPPD) disease is prevalent and has diverse presentations, but there are no validated classification criteria for this symptomatic arthritis. The American College of Rheumatology (ACR) and EULAR have developed the first-ever validated classification criteria for symptomatic CPPD disease., Methods: Supported by the ACR and EULAR, a multinational group of investigators followed established methodology to develop these disease classification criteria. The group generated lists of candidate items and refined their definitions, collected de-identified patient profiles, evaluated strengths of associations between candidate items and CPPD disease, developed a classification criteria framework, and used multi-criterion decision analysis to define criteria weights and a classification threshold score. The criteria were validated in an independent cohort., Results: Among patients with joint pain, swelling, or tenderness (entry criterion) whose symptoms are not fully explained by an alternative disease (exclusion criterion), the presence of crowned dens syndrome or calcium pyrophosphate crystals in synovial fluid are sufficient to classify a patient as having CPPD disease. In the absence of these findings, a score >56 points using weighted criteria, comprising clinical features, associated metabolic disorders, and results of laboratory and imaging investigations, can be used to classify as CPPD disease. These criteria had a sensitivity of 92.2% and specificity of 87.9% in the derivation cohort (190 CPPD cases, 148 mimickers), whereas sensitivity was 99.2% and specificity was 92.5% in the validation cohort (251 CPPD cases, 162 mimickers)., Conclusion: The 2023 ACR/EULAR CPPD disease classification criteria have excellent performance characteristics and will facilitate research in this field., (© 2023 The Authors. Arthritis & Rheumatology published by Wiley Periodicals LLC on behalf of American College of Rheumatology.)

Background: The Calcium Pyrophosphate Deposition (CPPD) subgroup of the Outcome Measures in Rheumatology (OMERACT) Ultrasound working group was established to validate ultrasound as an outcome measure instrument for CPPD, and in 2017 has developed and validated standardised definitions for elementary lesions for the detection of calcium pyrophosphate crystals in joints. The aim of this study was to develop and evaluate the reliability of a consensus-based ultrasound scoring system for CPPD extent, representing the next phase in the OMERACT methodology., Methods: In this study the novel scoring system for CPPD was developed through a stepwise process, following an established OMERACT ultrasound methodology. Following a previous systematic review to gather available evidence on existing scoring systems for CPPD, the novel scoring system was developed through a Delphi survey based on the expert opinion of the members of the OMERACT Ultrasound working group-CPPD subgroup. The reliability of the scoring system was then tested on a web-based and patient-based exercise. Intra-reader and inter-reader reliability of the new scoring system was assessed using weighted Light's κ coefficients., Findings: The four-grade semiquantitative scoring system consisted of: grade 0 (no findings consistent with CPPD), grade 1 (≤3 single spots or 1 small deposit), grade 2 (>3 single spots or >1 small deposit or ≥1 larger deposit occupying ≤50% of the structure under examination in the reference image-ie, the scanning view with the highest grade of depositions), and grade 3 (deposits that occupy more than 50% of the structure under examination in the reference image). The score should be applied to the knee (menisci and hyaline cartilage) and the triangular fibrocartilage complex of the wrist. The intra-reader and inter-reader reliabilities on static images were almost perfect (κ 0·90 [95% CI 0·79-1·00] and κ 0·84 [0·79-0·88]), and on the eight patients recruited (four [50%] female and four [50%] male) were substantial (κ 0·72 [95% CI 0·47 to 0·96] and 0·66 [0·61 to 0·71])., Interpretation: This OMERACT ultrasound scoring system for CPPD was reliable on both static images and patients. The scoring system might be a valuable tool for ensuring valid and comparable results in clinical trials and could help monitor the extent of crystal deposition in patients with CPPD in clinical practice., Funding: The Italian Ministry of Health - Ricerca Corrente., Competing Interests: Declaration of interests We declare no competing interests., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Fibromyalgia (FM) is a chronic syndrome characterised by widespread pain that affects millions of people worldwide. This article discusses various aspects of FM described in scientific papers published in 2022 and indexed in the PubMed database, including the most recent diagnostic acquisitions (especially in relation to the juvenile form of FM), risk factors, co-morbidities and objective measures. Emphasis is placed on the importance of identifying FM early and improving diagnostic methods (e.g. physical measurements, including walking test performance, hand grip force, and autonomic tests). The article also considers hypotheses concerning the pathophysiology of FM, including the role of inflammation, gut dysbiosis, and neuroinflammation, and possible treatment options, including medications such as antioxidants and kinin antagonists, neurostimulation, and mind-body interventions. Although ketamine, vitamin D, and hormone therapy have shown promise in reducing FM symptoms, further research is needed to optimise their use. Neurostimulation techniques, such as transcutaneous electrical nerve stimulation, transcranial direct-current stimulation and transcranial magnetic stimulation, have been investigated in terms of their efficacy in reducing pain and improving the quality of life. Finally, the role of nutrition is discussed as study findings suggest that weight control, modified high-antioxidant diets, and nutritional supplementation can help to alleviate the symptoms of FM.

Purpose of Review: Clinical manifestations of calcium pyrophosphate deposition (CPPD) disease are quite heterogeneous, ranging from asymptomatic presentation to severe forms of arthritis. In recent years, imaging, particularly ultrasound (US) has gained a central role for the diagnosis of CPPD. However, many questions are still open. Aim of this review is to present how US could be a key tool in the diagnosis and assessment of CPPD and for the identification of subsets of the disease., Recent Findings: awareness and research interest around CPPD is increasing in the recent years, as several international taskforces are working on the validation of outcome measures and classification criteria for CPPD, but many pieces of the puzzle are still missing. Recent studies demonstrated that CPPD is an underdiagnosed disease, frequently misdiagnosed as rheumatoid arthritis or polymyalgia rheumatica. US has been increasingly used in the past decade for the diagnosis of CPPD and US definitions have been validated by the OMERACT US working group in the recent years, making of US a valuable tool for diagnosis., Summary: The most challenging aspects of CPPD are the differential diagnosis with other form of arthritis of the elderly, and the classification of patients in clinical subsets. In this review, we will present the available data for the use of US in the diagnosis of CPPD and we will provide a mainly experienced-based approach to the potential role of the technique in differential diagnosis and phenotypization of patients., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)