[Late onset spondyloarthropathy misdiagnosed as polymyalgia rheumatica]

[18F]FDG-PET/CT in Polymyalgia Rheumatica: An Update and Future Aspects

Polymyalgia rheumatica (PMR) is an inflammatory disorder usually diagnosed in patients older than 50 years of age. It is characterized by sudden onset pain and prolonged morning stiffness in the scapular and/or pelvic girdle, sometimes debilitating and accompanied by constitutional symptoms such as weight loss. In approximately 20% of the cases, it is linked to giant cell arteritis (GCAV) representing a disease continuum. The diagnosis is mainly clinical and noninvasive imaging such as ultrasound of joints may be helpful. In atypical PMR cases, whole body imaging using [18F]FDG-PET/CT may be useful. First, to confirm or rule out the diagnosis of PMR, secondly, to assess the coexistence of a GCA, and thirdly to establish the differential diagnosis with other types of arthritides encountered in this age group, such as elderly-onset rheumatoid arthritis, spondyloarthropathies, crystal-induced arthropathies or the rare remittent seronegative symmetrical synovitis with pitting edema. Relatively typical patterns of [18F]FDG-PET/CT are well known, based on the clinical distribution of the disease (eg, scapular and pelvic girdle, interspinous bursae, sterno-costoclavicular joints, entheses), especially the hypermetabolism at the interspinous lumbar bursae that has shown the best post-test likelihood ratio in a meta-analysis. This article focuses on the differential diagnosis and on the visual and semi-quantitative tools that can be used to guide to the correct diagnosis of PMR as an add-on to the clinical picture. Further, we briefly discuss the options that can improve molecular imaging in the future for inflammatory rheumatisms in elderly.

PET/CT in Inflammatory and Auto-immune Disorders: Focus on Several Key Molecular Concepts, FDG, and Radiolabeled Probe Perspectives

Chronic immune diseases mainly include autoimmune and inflammatory diseases. Managing chronic inflammatory and autoimmune diseases has become a significant public health concern, and therapeutic advancements over the past 50 years have been substantial. As therapeutic tools continue to multiply, the challenge now lies in providing each patient with personalized care tailored to the specifics of their condition, ushering in the era of personalized medicine. Precise and holistic imaging is essential in this context to comprehensively map the inflammatory processes in each patient, identify prognostic factors, and monitor treatment responses and complications. Imaging of patients with inflammatory and autoimmune diseases must provide a comprehensive view of the body, enabling the whole-body mapping of systemic involvement. It should identify key cellular players in the pathology, involving both innate immunity (dendritic cells, macrophages), adaptive immunity (lymphocytes), and microenvironmental cells (stromal cells, tissue cells). As a highly sensitive imaging tool with vectorized molecular probe capabilities, PET/CT can be of high relevance in the management of numerous inflammatory and autoimmune diseases. Relying on key molecular concepts of immunity, the clinical usefulness of FDG-PET/CT in several relevant inflammatory and immune-inflammatory conditions, validated or emerging, will be discussed in this review, together with radiolabeled probe perspectives.

Use of 18F FDG PET-CT to discriminate polymyalgia rheumatica and atypical spondylarthritis in clinical practice

OBJECTIVE

To evaluate the relevance of ¹⁸F-labeled fluorodeoxyglucose-positron emission tomography/computed tomography (¹⁸F-FDG PET-CT) for discriminating polymyalgia rheumatica (PMR) and spondylarthritis (SpA) in atypical presentations.

METHODS

In 2 rheumatology departments, we identified PMR and atypical SpA patients who underwent ¹⁸F-FDG PET-CT and compared the 2 groups. The relevant ¹⁸F-FDG PET-CT findings identified on univariate analyses as discriminant for both groups were entered into a multivariable logistic regression model to derive a composite musculoskeletal score.

RESULTS

Between September 2012 and August 2018, we enrolled 35 PMR and 27 SpA patients (median [interquartile range] age 71 years [63.5-74.5] and 54 years [41.5-63], p < 0.001). ¹⁸F-FDG uptake in enthesis/bursae was more frequent in PMR than SpA (ischial tuberosities: 88.6% vs 48.1%, p < 0.001; interspinous processes: 91.4% vs 51.9%, p < 0.001). ¹⁸F-FDG uptake in sacroiliac joints was specific to SpA but rare (14.8% vs 0 in PMR, p < 0.05). The intensity of ¹⁸F-FDG uptake was similar in both conditions. The musculoskeletal score, including ¹⁸F-FDG uptake of the shoulders, ischial tuberosities and interspinous process, was higher for PMR than SpA patients (2.74 vs 1.11, p < 0.001). A score ≥ 2 provided sensitivity and specificity of 74.1% and 77.1% for the diagnosis of PMR.

CONCLUSION

¹⁸F-FDG PET-CT patterns of atypical SpA and PMR widely overlap, so differentiating the conditions is challenging. The use of the proposed PET-CT composite score could improve the diagnostic performance of ¹⁸F-FDG PET-CT to discriminate these 2 entities in clinical practice.

Diagnosis of polymyalgia rheumatica in primary health care: favoring and confounding factors - a cohort study

Objectives

To evaluate in a primary care setting the favoring and confounding factors for the diagnosis of polymyalgia rheumatica (PMR).

Material and methods

Among 303 patients consecutively referred by their general practitioners (GPs) to our rheumatologic outpatient clinic, we identified three groups: group A – patients with confirmed diagnosis of PMR, group B – patients with unconfirmed diagnosis, group C – patients with unrecognized PMR. All the diagnostic confounding and favoring factors were discussed with GPs using an e-mail questionnaire. Participation in rheumatology training courses represented the final question. The collected data were statistically assessed in a blind way. In Fisher’s exact test and ANOVA test, a p-value was significant if < 0.05. The study was carried out in compliance with the Helsinki Declaration and approved by the Ethics Committee of Mariano Lauro Hospital. Every patient signed an informed consent form at the time of the first visit.

Results

All patients were Caucasian; 24.1% were male; mean age was 72.3 ±8.6 years (min. – 51, max. – 94). There were 41 patients in group A, 93 in group B and 169 in group C. The percentage of misdiagnoses was very high (87.1%): among 134 patients diagnosed with PMR by their GPs (group A + group B) confirmation was made in 41, and in 169 unrecognized PMR was found. Participation in training courses was very significant compared to the diagnostic accuracy (p < 0.0001 in χ² test) and to the diagnosis timing (24.3 days ±12.5 vs. 42.9 ±15.5 with p-value < 0.05 in the ANOVA test). When the percentages were assessed according to participation, an inadequate evaluation of some clinical manifestations favored over-diagnosis among the trained GPs.

Conclusions

The level of diagnostic accuracy for PMR must be improved in primary care. Participation in rheumatology training courses can be an important step.

Performance of the classification criteria in patients with late-onset axial spondyloarthritis

AIM

To evaluate the performance of four different classification criteria for spondyloarthritis (SpA) in patients with late-onset symptoms and to compare the clinical, laboratory and radiographic outcomes among the patients with symptoms before and after 45 years of age.

PATIENTS AND METHODS

A total of 329 patients with SpA were enrolled in this prospective cohort. Patients with psoriatic arthritis, reactive arthritis, colitis associated arthritis and peripheral or undifferentiated SpA were excluded. The remaining individuals were divided into two groups based on their ages at the time of onset of symptoms: from 16 to 45 years of age (adult-onset, A-O) and after 45 years of age (late-onset, L-O). The clinical data were collected, including BASDAI, BASFI, BASMI, mSASSS, ASDAS, as were concomitant diseases and medications, efficacy and safety data. The performance of four SpA classification criteria, including modified New York, ESSG, Amor and ASAS, was evaluated in both groups. p value <.05 was considered as significant.

RESULTS

Thirty-two patients (9.72%) had L-O axial SpA. Mean age of diagnosis and symptoms were 57.6 (8.0) years and 7.6 (5.1) years, respectively. L-O patients had statistically worse functional impairment and higher disease activity. However, they had lower radiographic sacroiliac and spine damage (p < .001).

CONCLUSION

Our data showed that almost 10% of the patients with SpA had late-onset of symptoms. Moreover, they had higher disease activity, worse physical function and lower spine radiographic damage than A-O SpA patients. Additionally, the ASAS classification criteria had the best performance and might be used in clinical practice.