Acute Inflammatory Arthropathy and Hypercalcemia Leading to a Diagnosis of Primary Hyperparathyroidism in a Patient With Known Sarcoidosis.

Calcium pyrophosphate deposition disease (CPPD) is a crystal-induced arthropathy characterized by calcium pyrophosphate crystal deposition in joints and soft tissues. The diagnosis is suggested by the presence of chondrocalcinosis on x-ray but is most often diagnosed by synovial fluid analysis (SFA). CPPD is associated with aging and metabolic disorders such as hyperparathyroidism. In this case, we present an 87-year-old woman with known sarcoidosis who presented with acute arthropathy, hypercalcemia, and radiographic evidence of CPPD. Her hypercalcemia had been attributed to her sarcoidosis in the past without a full workup. Hypercalcemia in the setting of suspected CPPD led to a full workup for hypercalcemia and ultimately led to a diagnosis of primary hyperparathyroidism. This case highlights the importance of a complete evaluation for hypercalcemia in the setting of CPPD, even when another disease, such as sarcoidosis, could explain hypercalcemia. Ultimately, CPPD aided in diagnosing hyperparathyroidism in our patient with known sarcoidosis.

Monosodium urate crystals alter the circadian clock in macrophages leading to loss of NLRP3 inflammasome repression: Implications for timing of the gout flare.

Gout is caused by monosodium urate (MSU) crystal deposition within joints. This leads to acute episodes of inflammation ("gout flares") driven by NLRP3 inflammasome activation in macrophages. Gout flares are frequently present during late night/early morning. The reason for this timing is unclear. Recent evidence suggests the NLRP3 inflammasome is under circadian control. The purpose of this study was to determine whether MSU crystals cause changes in the circadian clock in macrophages leading to time-of-day differences in NLRP3 inflammasome activation. Levels of circadian clock components were measured in undifferentiated "monocytic" and PMA-differentiated "macrophagic" THP-1 cells cultured with/without MSU crystals. Caspase-1 activity was measured to assess NLRP3 inflammasome activity. MSU crystal exposure resulted in minimal effects on clock genes in THP-1 monocytes but BMAL1, CRY1, PER2, and REV-ERBα showed altered expression with reduced protein levels of BMAL1 and REV-ERBα in THP-1 macrophages. REV-ERBα activation or BMAL1 over-expression resulted in reduced MSU crystal-induced caspase-1 activity. BMAL1 knockdown resulted in a further increase in MSU crystal-induced caspase-1 activity, but only at times of day when BMAL1 levels were naturally high. MSU crystal-induced NLRP3 inflammasome activation was greatest at the time of day when BMAL1 levels were naturally low. MSU crystals alter the expression of circadian clock components in THP-1 macrophages leading to loss of BMAL1 and REV-ERBα-mediated repression of NLRP3 inflammasome activity and time-of-day differences in susceptibility to inflammasome activation. Our findings suggest that the nocturnal risk of gout flare is at least partially a consequence of altered circadian control of immune cell function.

Synovium to Myocardium: A Case of Calcium Pyrophosphate Dihydrate Crystal Arthritis Associated With Myocardial Infarction.

Both gout and pseudogout are crystal-induced arthropathies. Here, we report a case of acute calcium pyrophosphate dihydrate (CPPD) arthritis associated with type 1 myocardial infarction (MI). An 83-year-old female presented to our emergency department with generalized weakness and bilateral lower extremity edema. Her left foot was noted to be more inflamed compared to the right, with cardinal signs of pain, swelling, erythema, and warmth. A presumptive diagnosis of cellulitis was made, and antibiotics were initiated. Further investigations revealed elevated troponins with new-onset bundle branch block, ST, and T-wave changes on electrocardiogram, indicating a type 1 MI. After a review of the patient's history, imaging of the extremity, elevated inflammatory markers, and the typical distribution and pattern of inflammation, the diagnosis was changed to pseudogout. Steroids and colchicine were initiated, providing instant relief. This case highlights a possible association between cardiovascular disease and pseudogout, emphasizing the need for further studies regarding this relationship. Despite being rare, physicians should be made aware of this relationship, especially in patients with a history of CPPD arthritis presenting with type 1 MI.

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.

Confusion With Presentations of Calcium Pyrophosphate Dihydrate Disease: A Report of Two Cases Mistaken for Cellulitis.

Both pseudogout and cellulitis are diseases that may mimic one another in clinical practice. We discuss two cases of acute calcium pyrophosphate dihydrate (CPPD) arthritis mistaken for cellulitis in the emergency department. Both patients experienced significant improvement after management was changed to treat CPPD. These cases highlight how it is essential for physicians to consider CPPD as a differential diagnosis for a patient that is presenting with signs of inflammation in any joint.

Assessing tophaceous spinal gout treatment response using dual-energy CT as a point-of-care imaging modality: case report.

We describe a case of chronic tophaceous gout affecting the spine, hands, elbows, feet, and knees in a 67-year-old man with serum urate levels at 549 µmol/L whose response to treatment was successfully mapped using dual-energy computed tomography (DECT). The patient presented with exacerbation of acute-on-chronic lumbar back pain. He had received a diagnosis of gout 3 years prior to this presentation yet was not on any urate-lowering therapy. The patient received febuxostat 80 mg and colchicine 0.3 mg once daily and underwent DECT to assess baseline monosodium urate (MSU) burden. At baseline, MSU deposits were seen in the hands, elbows, feet, knees, and lumbar spine including the left L5-S1 facet joint encroaching onto the neural foramen. After 2.5 years of treatment, serum urate level was within the target range (< 360 µmol/L), and the patient underwent a follow-up DECT that revealed almost full resolution of MSU deposition in the spine, including the MSU-burdened facet joint and neural foramen in the lumbar spine, in addition to all the affected peripheral joints. This case is the first report of radiological evidence of nearly complete resolution of MSU deposits in spinal gout on DECT after urate-lowering therapy treatment, which demonstrates the utility of this imaging modality as a non-invasive investigational point-of-care imaging modality for mapping treatment response and identifying the etiology of back pain in a patient with chronic tophaceous spinal gout.

Management of temporomandibular joint diseases: a rare case report of coexisting calcium pyrophosphate crystal deposition and synovial chondromatosis.

BACKGROUND: The coexistence of calcium pyrophosphate dihydrate crystal deposition (CPP) and synovial chondromatosis (SC) in the temporomandibular joint (TMJ) is rarely reported. CPP disease (CPPD) is complex arthritis synonymous with excessive pyrophosphate production and variable aberrations in mineral and organic phase metabolism of the joint cartilage, leading to local inundated CPP and crystal deposition of partially deciphered predispositions. Meanwhile, SC is a rare benign synovial joint proliferative disease of unclear etiology and has a low risk of malignant transformation. However, SC manifests severe joint disability and dysfunction because of connective tissue metaplasia of the synovial membrane, which forms cartilaginous nodules with or without calcifications or ossifications. These nodules often detach and form intra-articular loose bodies and very rarely within extraarticular spaces. CASE PRESENTATION: We report the case of a 61-year-old man to expand the body of literature on these unusual coexisting arthropathies of the TMJ. The patient presented to our hospital in 2020 with complaints of pain in the right TMJ and trismus for over 6 months. Radiographic assessments of the TMJ provided a preoperative provisional diagnosis of SC. However, the histopathology of the open biopsy revealed tumor-like lesions comprising several deposits of rhomboid and rod-shaped crystals that displayed positive birefringence in polarized light, confirming a coexistence of CPPD. A second-stage operation was performed for the complete removal of the loose bodies and chalk-like lesions including synovectomy. No evidence of recurrence was recorded after a follow-up of nearly 1.5 years. CONCLUSIONS: Isolated CPPD and SC of the TMJ are prevalent in the literature however, monoarticular coexistence of these diseases is rare, due to the lack of consistency in the diagnostic criteria in clinical practice. Moreover, optimal treatment depends on several considerations. This report delineated the molecular etiopathology and underscored the need for continued deciphering of the causal mechanisms of coexisting CPPD and SC of the TMJ. In addition, the importance of confirmatory testing for accurate diagnosis, and appropriate management of these diseases were discussed.

Calcium pyrophosphate dihydrate crystal deposition disease and retro-odontoid pseudotumor rupture managed via posterior occipital cervical instrumented fusion: illustrative case.

BACKGROUND: Craniocervical junction and subaxial cervical spinal manifestations of calcium pyrophosphate deposition disease are rarely encountered. The authors presented a severe case of retro-odontoid pseudotumor rupture causing rapid quadriparesis and an acute comatose state with subsequent radiographic and clinical improvement after posterior occipital cervical fusion. OBSERVATIONS: The authors surveyed the literature and outlined multiple described operative management strategies for compressive cervical and craniocervical junction calcium pyrophosphate deposition disease manifestations ranging from neck pain to paresthesia, weakness, myelopathy, quadriparesis, and cranial neuropathies. In this report, radiographic features of cervical and craniocervical junction calcium pyrophosphate deposition disease were explored. Several previously described surgical strategies were compiled, including patient characteristics and outcomes. LESSONS: With this case report, the authors presented for the first time an isolated posterior occipital cervical fusion for treatment of a compressive retro-odontoid pseudotumor with rupture into the brainstem. They demonstrated rapid clinical and radiographic resolution after stabilization of cranial cervical junction only 12 weeks postsurgery.

Imaging of Crystal Disorders:: Calcium Pyrophosphate Dihydrate Crystal Deposition Disease, Calcium Hydroxyapatite Crystal Deposition Disease and Gout Pathophysiology, Imaging, and Diagnosis.

Crystal arthropathies are a group of joint disorders due to deposition of crystals in and around joints that lead to joint destruction and soft tissue masses. Clinical presentation is variable and diagnosis might be challenging. In this article the pathophysiology is addressed, the preferred deposition of crystal arthropathies and imaging findings. Case studies of calcium pyrophosphate dihydrate crystal deposition disease, hydroxyapatite crystal deposition disease, and gout are shown. Guidelines for the use of dual-energy computed tomography are given to enable the diagnosis and follow-up of gout.

The Ultrasound-guided Anteromedial Joint Line Approach: A Targeted Corticosteroid Injection Technique for Patients With Medial Knee Pain.

BACKGROUND: Medial knee pain is a common complaint in the adult population. When conservative measures fail, intraarticular knee corticosteroid injections are often offered through the superolateral approach into the suprapatellar recess to provide short-term relief. However, some patients fail to respond and require alternative approaches. The anteromedial joint line (AMJL) approach, which targets the medial compartment, may be more effective when pain-generating pathologies such as synovitis are located in the medial compartment. To date, there have been no dedicated studies evaluating ultrasound-guided (USg) corticosteroid injections through the AMJL approach to reduce medial knee pain. OBJECTIVES: The current study aims to assess the clinical characteristics, ultrasound findings, and clinical outcomes for patients with medial knee pain who received USg corticosteroid injections via the AMJL approach. STUDY DESIGN: Retrospective study. SETTING: This study took place at one academic musculoskeletal ultrasound clinic at an urban tertiary care center. METHODS: Sixty-five patients (76 knees; 11 patients with bilateral injections) with medial knee pain who had received USg-AMJL corticosteroid injections from January 2016 through  March 2020 were reviewed for inclusion. Baseline demographic information and clinical characteristics from one year prior to 6 months following USg-AMJL injection were analyzed for each patient. Responders were defined as those who reported pain relief, decreased usage of analgesic medications, or increased physical activity. Nonresponders  were defined as those not meeting any of the responder endpoints. RESULTS: Within one year prior to receiving a USg-AMJL injection, 51.3% (39/76 knees) had attempted superolateral knee injections without relief. Immediately following a USg-AMJL injection, 98.7% (75/76) experienced symptomatic relief. Follow-up visits took place on average at 11 weeks postinjection with 92.3% (60/65 patients) responding positively. In comparison to the responder group, the nonresponder group had a significantly older mean age (P = 0.009), lower mean body mass index (P = 0.007), and higher burden of morbidities as measured by the Charlson Comorbidity Index (P = 0.044). One patient reported a steroid flare within one week of injection. The most common diagnoses contributing to medial knee pain for these patients were osteoarthritis, medial meniscal injury, crystal arthropathy, and medial collateral ligament injury, which were supported by point-of-care ultrasound findings. LIMITATIONS: This study was limited by its sample size and retrospective observational design. CONCLUSIONS: USg AMJL injection is a safe and effective procedure for targeting medial knee pain, particularly in the settings of obesity and prior failed superolateral and suprapatellar knee injections. Further investigation is required to assess long-term clinical outcomes of this injection approach.

Management of a Hot Swollen Joint in the Acute Setting.

BACKGROUND: The presentation of a hot swollen joint is common in the emergency department, general practice, rheumatology and orthopedic clinics. There is a wide set of differential diagnoses for a hot swollen joint, thus making it difficult to diagnose and manage, especially for junior doctors. Initially, it is pertinent to exclude/diagnose medical and surgical emergencies. OBJECTIVE: This paper aims to summarize the key indications within the history, examination and investigations in order to quickly and effectively diagnose a hot swollen joint based on the original 2006 management guidelines and the papers discussing other possible indications and management strategies published since then. RESULTS: Currently, the management of crystal and non-infectious arthropathies is well recognized with little disparity. However, the treatment of infectious arthritis is not concrete, and there are discrepancies in management between doctors. CONCLUSION: We have summarized the key indications and provided a diagnostic flow chart to aid with the management of a hot swollen joint.

Crystalline-Induced Arthropathy Following Total Knee Replacement.

Gout rarely occurs in the setting of prior total joint replacement. It can present as an acute or chronic painful joint that may mimic prosthetic joint infection with further similarities found on physical examination and initial workup. Elevated leukocyte count, erythrocyte sedimentation rate, and C-reactive protein are common to both conditions. The confirmatory test to distinguish infection versus inflammatory arthropathy is joint aspiration with crystal or micro-organism identification microscopically. Establishing proper diagnosis is important in guiding appropriate treatment, which may prevent the unnecessary removal of implants. The current study includes a review of the literature and presents a case of bilateral gouty arthropathy after total knee arthroplasty.

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.

Images in Primary Care Medicine: Point-of-Care Ultrasound in Gout.

Gout is the most common crystal arthropathy and is frequently diagnosed and managed by primary care physicians. Point-of-care ultrasound (POCUS) is a valuable tool to aid in the diagnosis of gout via the identification of the double contour sign, aggregates of crystals, tophi, and erosions. In addition, POCUS can aid in the management of gout by recognizing early signs of gout, monitoring the effectiveness of urate-lowering therapy, and guiding aspiration and corticosteroid injection.

Gout and 'Podagra' in medieval Cambridge, England.

OBJECTIVE: To estimate the prevalence rate of gout and to explore the social factors that contributed to its development in the various sub-populations in medieval Cambridge. MATERIALS: 177 adult individuals from four medieval cemeteries located in and around Cambridge, UK. METHODS: Lesions were assessed macroscopically and radiographically. Elements with lytic lesions were described and imaged using micro-computed tomography (µCT) to determine their morphology. RESULTS: Gout was identified in 3 % of the population. Individuals buried in the friary had highest prevalence (14 %), with low prevalence rates in the Hospital (3 %) and town parish cemetery (2 %), with no cases in the rural parish cemetery. Gout was more prevalent during the 14th-15th centuries than the 10th-13th centuries. CONCLUSION: The high prevalence rate of gout in the friary is at least partly explained by the consumption of alcohol and purine-rich diets by the friars and the wealthy townsfolk. Medieval medical texts from Cambridge show that gout (known as podagra) was sometimes treated with medications made from the root of the autumn crocus. This root contains colchicine, which is a medicine that is still used to treat gout today. SIGNIFICANCE: This is one of the first studies to assess the epidemiology of gout in medieval England and suggests that gout varied with social status. LIMITATIONS: Our sample size precludes statistical analysis. SUGGESTIONS FOR FURTHER RESEARCH: Additional studies that assess the epidemiology of gout in medieval Europe is needed in order to be able to fully contextualize these findings.

The diagnostic value of conventional radiography and musculoskeletal ultrasonography in calcium pyrophosphate deposition disease: a systematic literature review and meta-analysis.

OBJECTIVE: To examine and compare the accuracy of conventional radiography (CR) and musculoskeletal ultrasonography (US) in the diagnosis of calcium pyrophosphate (CPP) crystals deposition disease (CPPD). DESIGN: A systematic search of electronic databases (PubMed, Embase, and Cochrane), conference abstracts and reference lists was undertaken. Studies which evaluated the accuracy of CR and/or US in the diagnosis of CPPD, using synovial fluid analysis (SFA), histology or classification criteria as reference tests were included. Subgroup analyses by anatomic site and by reference test were performed. RESULTS: Twenty-six studies were included. Using SFA/histology as reference test, CR and US showed an excellent (CR AUC = 0.889, 95%CI = 0.811-0.967) and an outstanding (US AUC = 0.954, 95%CI = 0.907-1.0) diagnostic accuracy (p < 0.01), respectively. Furthermore, US showed a higher sensitivity (0.85, 95%CI = 0.79-0.90 vs 0.47, 95%CI = 0.40-0.55) and only a little lower specificity (0.87, 95%CI = 0.83-0.91 vs 0.95, 95%CI = 0.92-0.97) than CR. A considerable heterogeneity between the studies was found, with adopted reference test being the main source of heterogeneity. In fact, subgroup analysis showed a significant change in the diagnostic accuracy of CR, but not of US, using Ryan and McCarty criteria or SFA/histology as reference test (CR: AUC = 0.956, 95%CI = 0.925-1.0 vs AUC = 0.889, 95%CI = 0.828-0.950, respectively, p < 0.01) (US: AUC = 0.922, 95%CI = 0.842-1.0 vs AUC = 0.957, 95%CI = 0.865-1.0, respectively, p = 0.08) CONCLUSIONS: Although US is more sensitive and a little less specific than CR for identifying CPP crystals, both these two techniques showed a great diagnostic accuracy and should be regarded as complementary to each other in the diagnostic work-up of patients with CPPD.

[Slowly progressive joint destruction in an older man as expression of hydroxyapatite disease. Case report and literature review]. / Langsam progrediente Gelenkzerstörung bei einem älteren Mann als Ausdruck einer Hydroxylapatiterkrankung. Fallbericht und Literaturübersicht.

This article reports the case of a 75-year-old male patient presenting with arthralgia of the large joints that had existed for 10 years. Clinically, bursitis of the right elbow joint was found. Laboratory tests showed elevated inflammatory markers and imaging revealed erosive joint destruction. A surgical bursectomy was performed. Histologically, hydroxyapatite crystals were detected in alizarin red S staining and a crystal arthropathy was diagnosed. The diagnostics are difficult since crystals can only be detected by electron microscopy or special staining methods.

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.

Prevalence and incidence of non-gout crystal arthropathy in southern Sweden.

OBJECTIVE: To estimate the prevalence and incidence of non-gout crystal arthropathy in relation to socioeconomic factors in southern Sweden. METHODS: All patients (age ≥ 18 years) with at least one visit to a physician with the diagnosis of interest in the Skåne region (population of 1.3 million) in 1998-2014 were identified. Non-gout crystal arthropathy (ICD-10 codes M11.0-M11.9) was subclassified in four different groups: calcium pyrophosphate crystal deposition related arthropathy (CPPD), unspecified non-gout arthropathies, chondrocalcinosis, and hydroxyapatite crystal deposition disease. The crude and age-adjusted point prevalence on December 31, 2014, and the cumulative incidence during 2014 were calculated for all non-gout crystal arthropathies, CPPD, and other unspecified non-gout arthropathies overall and in relation to occupation, income, and level of education. RESULTS: The crude 2014 point prevalence (95% CI) and 2014 cumulative incidence (95% CI) of all non-gout crystal arthropathies were 0.23% (0.23-0.24) and 21.5 (19-25) cases/100,000 persons. Mean age (range) among all prevalent cases in 2014 was 71 (20-102) years and 56% were males. The point prevalence and cumulative incidence of CPPD were 0.09% (0.08-0.09) and 8 (7-10)/100,000 persons, respectively. The corresponding data for unspecified non-gout crystal deposition disease was 0.16% (0.16-0.17) and 15.6 (13-18)/100,000 persons, respectively. The prevalence and incidence of CPPD and unspecified non-gout crystal arthropathies were slightly higher in men and increased with age irrespective of gender. Unspecified non-gout crystal arthropathy but not CPPD was less prevalent in persons with ≥ 15 years of education, whereas there were no clear associations with occupation and income. CONCLUSION: The prevalence of all diagnosed non-gout crystal arthropathies was 0.23%, thus considerably less prevalent than gout in southern Sweden. CPPD and other unspecified non-gout crystal arthropathies are the predominant diagnoses, increasing with age and in men. With the exception for unspecified non-gout crystal arthropathies being inversely correlated to a higher level of education, no convincing association with the socioeconomic factors was found.

Recent developments in advanced imaging in gout.

The plain radiographic features of gout are well known; however, the sensitivity of plain radiographs alone for the detection of signs of gout is poor in acute disease. Radiographic abnormalities do not manifest until late in the disease process, after significant joint and soft tissue damage has already occurred. The advent of dual-energy computed tomography (DECT) has enabled the non-invasive diagnosis and quantification of gout by accurately confirming the presence and extent of urate crystals in joints and soft tissues, without the need for painful and often unreliable soft tissue biopsy or joint aspiration. Specific ultrasound findings have been identified and may also be used to aid diagnosis. Both ultrasound and magnetic resonance imaging (MRI) may be used for the measurement of disease extent, monitoring of disease activity or treatment response, although MRI findings are nonspecific. In this article we summarize the imaging findings and diagnostic utility of plain radiographs, ultrasound, DECT, MRI and nuclear medicine studies in the assessment as well as the implications and utility these tools have for measuring disease burden and therapeutic response.