Reactive arthritis following COVID-19: clinical case presentation and literature review.

Reactive arthritis (ReA) is a clinical condition typically triggered by extra-articular bacterial infections and often associated with the presence of HLA-B27. While ReA has traditionally been associated with gastrointestinal and genitourinary infections, its pathogenesis involves immune and inflammatory responses that lead to joint affections. The emergence of COVID-19, caused by SARS-CoV-2, has prompted studies of plausible associations of the virus with ReA. We present a case of ReA in a patient who survived COVID-19 and presented with joint affections. The patient, a 31-year-old man, presented with lower limb joints pain. SARS-CoV-2 was confirmed by PCR testing during COVID-19-associated pneumonia. Following a thorough examination and exclusion of all ReA-associated infections, a diagnosis of ReA after COVID-19 was confirmed. In addition, this article encompasses a study of similar clinical cases of ReA following COVID-19 reported worldwide.

Reactive arthritis: the convoluted history of Reiter's disease.

Reactive arthritis, previously known as Reiter's Syndrome or Disease was a post-dysenteric, asymmetrical acute large joint polyarthritis, with fever, conjunctivitis, iritis, purulent urethral discharge, rash and penile soft tissue swelling. Although the eponym was given to Hans Reiter, various forms of the condition have been recorded in history a few hundred years before Reiter. Two French doctors, Noel Fiessinger (1881-1946) and Edgar Leroy (d. 1965), presented a paper at la Societe des Hopitaux-in Paris on the 8th December 1916 on dysentery in 80 soldiers on the Somme, and four of whom developed a "syndrome conjunctivo-uretro-synovial". Their paper was given 4 days before Reiter's presentation on 12th December 1916 at the Society of Medicine in Berlin, on a German army officer with an illness similar to those described by Fiessinger and Edgar Leroy. It is documented that Hans Reiter was one of a number of University professors who signed an oath of allegiance to Adolf Hitler in 1932. For socio-ethical reasons and for clinical utility, Reiter's syndrome is now known as reactive arthritis.

Spondyloarthropathies and arthritis post-infection: a historical perspective.

The spondyloarthropathies are a group of conditions characterised by spinal joint pain and have related clinical, epidemiological and genetic-related features. Ankylosing spondylitis, reactive arthritis, the spinal form of psoriatic arthritis and Crohn's and colitis enteropathic arthritis are the major clinical entities of the spondyloarthropathies, and principally occur in HLA-B27 positive individuals. Ankylosing spondylitis is much more common in males than females. Patients are usually seronegative for rheumatoid factor, and extra-articular features including iridocyclitis, mucous membrane and skin lesions: aortitis, may occur in some patients. The reactive arthritis form classically occurs following an infection of the gastrointestinal or genitourinary tract. The Crohn's and colitis enteropathic arthritis forms often have an associated large joint asymmetrical arthritis. Also discussed are acute rheumatic fever and Lyme disease which are conditions where the individual develops arthritis after an infection.

Reactive arthritis after COVID-19 vaccination: 17 cases.

OBJECTIVES: The aim of the study is to report a series of 17 cases of ankle bi-arthritis that occurred shortly after coronavirus disease 2019 RNA vaccination, and to discuss the potential role of these vaccines in the pathogenesis of this rheumatological manifestation. METHODS: All patients were examined in the same department and received a full work-up to investigate the usual causes of ankle bi-arthritis. No rheumatic inflammatory disease occurred after 9 months of follow-up. A post-vaccination serological follow-up in search of anti-Spike antibodies was requested for all patients. RESULTS: All patients recovered with low dose of prednisolone within <2 months, except one who could not be weaned off CS. The level of antibodies found was very high in all patients. CONCLUSION: The ankle bi-arthritis occurrence chronology, the follow-up and the similar clinical presentation might suggest a pathogenic role of RNA vaccination.

Reactive arthritis occurring after COVID-19 infection: a narrative review.

PURPOSE: Reactive arthritis is acute aseptic arthritis occurring 1 to 4 weeks after a distant infection in a genetically predisposed individual. It may occur after COVID-19 infection. We summarize, in this article, the current findings of reactive arthritis following COVID-19 infection. METHODS: A literature search has been performed from December 2019 to December 2021. We included case reports of reactive arthritis occurring after COVID-19 infection. We collected demographic, clinical, and paraclinical data. RESULTS: A total of 22 articles were reviewed. There were 14 men and 11 women with a mean age of 44.96 + 17.47 years. Oligoarticular involvement of the lower limbs was the most frequent clinical presentation. The time between arthritis and COVID infection ranged from 6 to 48 days. The diagnosis was based on clinical and laboratory findings. The pharmacological management was based on non-steroidal anti-inflammatory drugs in 20 cases. Systemic or local steroid therapy was indicated in 13 patients. Sulfasalazine was indicated in two cases. Alleviation of symptoms and recovery were noted in 22 cases. The mean duration of the clinical resolution was 16 + 57 days. CONCLUSION: The diagnosis of reactive arthritis should be considered in patients with a new onset of arthritis following COVID-19 infection. Its mechanism is still unclear.

Azacitidine as a rare cause of reactive arthritis in a patient with acute myeloid leukemia.

INTRODUCTION: Azacitidine (AZA), a demethylating agent, is one of the mainstay treatments for patients with myelodysplastic syndromes (MDS) and acute myeloid leukaemia (AML) who are ineligible for curative allogeneic stem-cell transplantation and is recommended as first-line treatment in multiple countries. While arthralgia and myalgia have been commonly reported as side effects, the incidence of drug-induced reactive arthritis has only been reported twice so far. CASE REPORT: We present a retrospective overview of a clinical case of a 71-year-old patient that developed new cytopenias on a background of Chronic Lymphocytic Leukaemia and was diagnosed with therapy-associated AML. His treatment included an indefinite course of AZA to induce remission and optimise long-term survival which resulted in a satisfactory haematological response. However, after his ninth AZA cycle, he presented to the emergency department with knee swelling and erythema and conjunctivitis. MANAGEMENT AND OUTCOMES: Arthrocentesis of the knee revealed reactive arthritis with no crystal or organism growth. His symptoms were managed effectively with conservative management including NSAIDs, analgesia and temporary immobilization for joint rest. The adverse drug reaction probability score in our study was calculated as six and adverse drug reaction was thus assigned to the "probable" category. CONCLUSION: We report a case that points to AZA as a probable cause of arthritis flares in MDS patients. The current limitation of this study is the lack of available data, future reviews and research will aid in providing stronger evidence of a correlation between arthritis and AZA treatment.

Multidisciplinary Team Led by Joint Surgeons to Rapidly Identify Spondyloarthritis.

Context: Spondyloarthritis (SpA) is a group of chronic, inflammatory, rheumatic diseases of which axial SpA and peripheral SpA are the two main types. Patients that predominantly have manifestations of axSpA may have additional peripheral-arthritis symptoms, and vice versa. For these hard-to-diagnose SpA patients, symptoms can be nonspecific and difficult to identify, making it easy to miss a diagnosis or misdiagnosis patients, resulting in disability. Objective: The study intended to evaluate the value of a multidisciplinary team (MDT) led by the joint surgeons to rapidly identify spondyloarthritis (SpA). Design: The research team designed a controlled study that analyzed the clinical data of patients with spondyloarthritis. Setting: The study was conducted in the Department of Joint Surgery at Shandong Second Provincial General Hospital in Jinan, China. Participants: Participants were 113 SpA patients at the hospital between January 2019 and January 2020. Intervention: he research team divided participants into an intervention group, the MDT group that used that model to diagnose 83 participants and the control group with 30 participants, for whom diagnoses occurred using the conventional diagnostic model. Outcome Measures: The research team collected data on participants' number of visits and number of departments visited as well as determined the amount of time that elapsed before a diagnosis occurred. The team also measured C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) and the scores on the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), and Bath Ankylosing Spondylitis Functional Index (BASFI) at baseline and after 3 months and 6 months treatment. Results: In the MDT group, diagnoses included: (1) axial SpA (axSpA)-73 participants, and (2) peripheral SpA-10 participants, including three with reactive arthritis, two with uveitis, and five with psoriatic arthritis. Eight participants in that group were HLA-B27 positive, and 14 had complications from a latent tuberculosis infection. In the control group, diagnoses included: (1) axSpA-25 participants; and (2) peripheral SpA-5 participants, including three with psoriatic arthritis and two with reactive arthritis. Six participants in that group were HLA-B27 positive and four had complications from a latent tuberculosis infection. The number of visits, number of departments visited, and time to diagnosis in the MDT group were significantly lower than those in the control group (P < .001). After three and six months of treatment, the MDT group's CRP, ESR, BASDAI, and BASFI were significantly lower than those at baseline (P < .001). Conclusions: The MDT model of spondyloarthritis led by joint surgeons was accurate and efficient, allowing the medical personnel to quickly identify and intervene in SpA and provide effective treatment for patients. It's a diagnosis and treatment model worthy of promotion.

Reactive arthritis following COVID-19: cause for concern.

Low-quality evidence suggests that COVID-19 may trigger reactive arthritis one to four weeks after the infection. Post COVID-19 reactive arthritis resolves within a few days, and no additional treatment is required. Established diagnostic or classification criteria for reactive arthritis are missing, and a deeper understanding of the immune mechanism related to COVID-19 prompt us to further investigate the immunopathogenic mechanisms capable of promoting or contrasting the development of specific rheumatic diseases. Caution should be exerted when managing post-infectious COVID-19 patient with arthralgia.

[Reactive arthritis]. / Reaktive Arthritis.

Reactive arthritis Abstract. Reactive Arthritis is a sterile, inflammatory arthritis that is typically preceded by a bacterial gastrointestinal or urogenital infection occurring one to four weeks previously. The typical pattern is an asymmetric oligoarthritis most common affecting the lower extremities. Similar to other spondyloarthropathies, enthesitis, dactylitis, and sacroiliitis can occur as well as extra-articular manifestations, such as conjunctivitis, anterior uveitis, oral ulcers, circinate balanitis, and keratoderma blennorrhagicum. The treatment of "triggering" infection with antibiotics is the first therapeutic goal, especially for Chlamydia trachomatis. For arthritis NSAIDs are the treatment of first choice, followed by intraarticular or oral glucocorticosteroids. DMARDs (Sulfasalzine, TNF-alpha inhibitors) are reserved for refractory cases. Over 50% of the patients have a self-limited course lasting two to six months, 30% have recurrent episodes, and 10-20% have a chronic course requiring immunosuppressive therapy.

Quo vadis reactive arthritis?

PURPOSE OF REVIEW: We provide an overview of recent articles which describe new thinking regarding HLA-B27-associated reactive arthritis (ReA), including those additional infection-related arthritides triggered by microbes that often are grouped under the term ReA. RECENT FINDINGS: With the advent and continuation of the pandemic, an increasing number of cases and case series of post-COVID-19 arthritis have been reported and classified as ReA. Further, arthritis after COVID-19 vaccination is a new entity included within the spectrum of ReA. New causative microorganisms identified in case reports include Clostridium difficile, Mycoplasma pneumoniae, Giardia lamblia, Leptospira , and babesiosis. SARS-CoV-2 is emerging as a significant etiologic agent for apparent ReA. SUMMARY: It is now clear that comprehensive clinical and laboratory investigations, synovial fluid analyses, and close follow-up of patients all are essential to differentiate ReA from diseases that may present with similar clinical attributes. Further, and importantly, additional research is required to define the wide diversity in causative agents, epidemiology, and rare case presentations of these arthritides. Finally, new classification and diagnostic criteria, and updated treatment recommendations, are essential to the advancement of our understanding of ReA.

Elucidating the role of a positive family history in differentiating between axial and peripheral spondyloarthritis: an ancillary analysis of the ASAS-PerSpA study.

OBJECTIVES: Positive family history (PFH) of spondyloarthritis (SpA) is important in the diagnosis of SpA. However, the contribution of a PFH in differentiating the two SpA subtypes (axial and peripheral spondyloarthritis (pSpA)), in particular the importance of second-degree relative (SDR) has not been well-studied. We aimed to investigate whether PFH of radiographic axial spondyloarthritis (r-axSpA), psoriasis, uveitis, reactive arthritis and inflammatory bowel disease in first-degree relative (FDR) and second-degree relative (SDR) contributes to differentiation between axSpA and pSpA using the data from a multinational cohort study. METHODS: The ASAS-PerSpA study dataset was used to assess the effects of a PFH on differentiating between axSpA and pSpA via generalised structural equation modelling. Model building using backward selection was performed to obtain a final model. Direct, indirect and total effects of the path analysis were calculated. RESULTS: A total of 3803 patients were included: 2458 axSpA and 1345 pSpA patients. FDR (OR: 3.75, 95% CI: 2.86-4.91, p<0.001) and SDR (OR: 4.58, 95% CI: 3.19-6.59, p<0.001) with r-axSpA were positively associated while FDR (OR: 0.262, 95% CI: 0.207-0.331, p<0.001) and SDR (OR: 0.305, 95% CI: 0.221-0.420, p<0.001) with psoriasis were negatively associated with differentiating patients with axSpA from pSpA. CONCLUSIONS: The presence of r-axSpA and psoriasis in FDR or SDR are useful in differentiating axSpA from pSpA. SDR with r-axSpA may contribute greater towards the differentiation than FDR. Clinicians should consider taking an extensive family history of SpA and their subtypes to better differentiate the subtypes within the SpA spectrum.

Dendritic Cells of Mesenteric and Regional Lymph Nodes Contribute to Yersinia enterocolitica O:3-Induced Reactive Arthritis in TNFRp55-/- Mice.

Dendritic cells (DCs) participate in the pathogenesis of several diseases. We investigated DCs and the connection between mucosa and joints in a murine model of Yersinia enterocolitica O:3-induced reactive arthritis (ReA) in TNFRp55-/- mice. DCs of mesenteric lymph nodes (MLN) and joint regional lymph nodes (RLN) were analyzed in TNFRp55-/- and wild-type mice. On day 14 after Y. enterocolitica infection (arthritis onset), we found that under TNFRp55 deficiency, migratory (MHChighCD11c+) DCs increased significantly in RLN. Within these RLN, resident (MHCintCD11c+) DCs increased on days 14 and 21. Similar changes in both migratory and resident DCs were also detected on day 14 in MLN of TNFRp55-/- mice. In vitro, LPS-stimulated migratory TNFRp55-/- DCs of MLN increased IL-12/23p40 compared with wild-type mice. In addition, TNFRp55-/- bone marrow-derived DCs in a TNFRp55-/- MLN microenvironment exhibited higher expression of CCR7 after Y. enterocolitica infection. The major intestinal DC subsets (CD103+CD11b-, CD103-CD11b+, and CD103+CD11b+) were found in the RLN of Y. enterocolitica-infected TNFRp55-/- mice. Fingolimod (FTY720) treatment of Y. enterocolitica-infected mice reduced the CD11b- subset of migratory DCs in RLN of TNFRp55-/- mice and significantly suppressed the severity of ReA in these mice. This result was associated with decreased articular IL-12/23p40 and IFN-γ levels. In vitro FTY720 treatment downregulated CCR7 on Y. enterocolitica-infected bone marrow-derived DCs and purified MLN DCs, which may explain the mechanism underlying the impairment of DCs in RLN induced by FTY720. Taken together, data indicate the migration of intestinal DCs to RLN and the contribution of these cells in the immunopathogenesis of ReA, which may provide evidence for controlling this disease.

Surgically treated reactive arthritis of the ankle after COVID-19 infection: A case report.

A 37-year-old man developed right ankle pain and swelling six days after being diagnosed with coronavirus disease (COVID-19). Despite conservative treatment, his ankle symptoms persisted. Magnetic resonance imaging and computed tomography showed synovial hypertrophy and bone erosion in the ankle. Following arthroscopic synovectomy, performed 69 days after the COVID-19 diagnosis, the pain improved significantly. The clinical course was consistent with that of reactive arthritis following severe acute respiratory syndrome coronavirus 2 infection. The pathological findings resembled rheumatoid nodules. The bone erosion may have originated from the inflammatory pathway, which resembles the mechanism of rheumatoid arthritis.

The potential value of fibrinogen to albumin ratio (FAR) in the assessment of inflammation in spondyloarthritis.

BACKGROUND: Fibrinogen to albumin ratio (FAR) is a newly investigated indicator for inflammation. The study aimed to explore the potential ability of FAR in assessing the severity of inflammation in spondyloarthritis. METHODS: The clinical data of 196 spondyloarthritis (SpA) patients, 66 osteoarthritis (OA) patients, and 81 healthy controls (HC) were collected in this retrospective study. The SpA group included 69 psoriatic arthritis patients, 47 reactive arthritis patients and 80 ankylosing spondylitis patients. Chi-square test and Mann-Whitney U test, Spearman's correlation test, regression analysis, and ROC analyses were used for the analysis of FAR. RESULTS: FAR level in group SpA was higher than in OA or HC. In the SpA group, the reactive arthritis group was characterized by the highest FAR level. After matching the erythrocyte sedimentation rate, a significant difference occurred between groups SpA and OA, but not in SpA subgroups. The FAR level was significantly related to erythrocyte sedimentation rate and C-reactive protein. After regression and receiver operating characteristics analysis, FAR was considered the most potential pointer to evaluate inflammation in SpA with the area under curve of 0.95. The recommended cut-off value of FAR was 9.44 for serious inflammation and 8.34 for mild conditions. CONCLUSION: FAR is closely related to inflammatory biomarkers and can be a potential indicator in the assessment of inflammation in spondyloarthritis.

Clinical profiles of post-infectious arthritis and transient synovitis of the hip in children.

BACKGROUND: Acute inflammatory arthritides can present as a result of immune reaction following infections. Post-infectious arthritis and transient synovitis of the hip in children are included in this disease entity. The aim of this study was to describe the clinical profiles of post-infectious arthritis and transient synovitis of the hip in Thai children. METHODS: A retrospective review was performed at a tertiary care hospital in Bangkok, Thailand from January 2005 to July 2017. RESULTS: Eighty-six patients (56 boys and 30 girls) were included in this study. Mean age was 8.4 ± 4.8 years. Reactive arthritis was diagnosed in two patients (2.3%) following Salmonella spp. and Chlamydia trachomatis infections. Post-streptococcal reactive arthritis was present in 10 patients (11.6%). Transient synovitis of the hip was found in 30 patients (34.9%). Forty-four patients (51.2%) were clinically diagnosed with post-infectious arthritis. Mono/oligoarthritis was the most common clinical profile (84.9%). The distribution of lower-extremity involvement was as follows: hip, 47.6%; knee, 46.5%; and ankle joints, 30.2%. The documented preceding illness consisted mostly of upper respiratory tract symptoms (30.2%). Non-steroidal anti-inflammatory drugs were prescribed for 70 patients (81.4%). CONCLUSION: Mono/oligoarthritis of the lower extremity was the main clinical profile. Preceding viral illness was documented in one-third of children. Reactive arthritis was rarely seen.

Knowledge and Perceptions of Reactive Arthritis Diagnosis and Management Among Healthcare Workers During the COVID-19 Pandemic: Online Survey.

BACKGROUND: Reactive arthritis (ReA) is an often neglected disease that received some attention during the coronavirus disease 2019 (COVID-19) pandemic. There is some evidence that infection with severe acute respiratory syndrome coronavirus 2 can lead to "reactive" arthritis. However, this does not follow the classical definition of ReA that limits the organisms leading to this condition. Also, there is no recommendation by any international society on the management of ReA during the current pandemic. Thus, a survey was conducted to gather information about how modern clinicians across the world approach ReA. METHODS: An e-survey was carried out based on convenient sampling via social media platforms. Twenty questions were validated on the pathogenesis, clinical presentation, and management of ReA. These also included information on post-COVID-19 arthritis. Duplicate entries were prevented and standard guidelines were followed for reporting internet-based surveys. RESULTS: There were 193 respondents from 24 countries. Around one-fifth knew the classical definition of ReA. Nearly half considered the triad of conjunctivitis, urethritis and asymmetric oligoarthritis a "must" for diagnosis of ReA. Other common manifestations reported include enthesitis, dermatitis, dactylitis, uveitis, and oral or genital ulcers. Three-fourths opined that no test was specific for ReA. Drugs for ReA were non-steroidal anti-inflammatory drugs, intra-articular injections, and conventional disease-modifying agents with less than 10% supporting biological use. CONCLUSION: The survey brought out the gap in existing concepts of ReA. The current definition needs to be updated. There is an unmet need for consensus recommendations for the management of ReA, including the use of biologicals.

[History of reactive arthritis. Historical milestones and future]. / Geschichte der reaktiven Arthritis. Historische Meilensteine und Zukunft.

The introduction of the term reactive arthritis (ReA) for the joint inflammation observed after infection with Yersinia enterocolitica, in which "a causative pathogen cannot be isolated from the synovial fluid", and the association with the HLA-B27 were the historical milestones for a new classification and assignment to the spondylarthritides (SpA). The division into postinfectious and reactive arthritis proposed in 1976 was put into perspective in the 1990s because of investigations with the newly available molecular biological method of the polymerase chain reaction. Microbial products could be identified from joint samples of patients with ReA. Therefore, it was proposed to abandon the distinction between the two groups of diseases and to prefer the term ReA for both. This created a terminological and nosological issue. On the one hand, there are generally accepted classification and diagnostic criteria for the classical HLA-B27-associated ReA that are assigned to SpA. On the other hand, an increasing number of bacterial pathogens, viruses, amoebas, helminths as well as antiviral and antibacterial vaccinations are described as triggers of arthritis, which have been published under the term ReA. Since the beginning of the SARS-CoV­2 pandemic, cases of acute post-COVID-19 arthritis have been described, which were also classified as ReA because of comparable clinical features.

Reactive Arthritis After Intravesical Bacillus Calmette-Guérin Therapy.

ABSTRACT: Reactive arthritis (ReA) is a sterile arthritis that occurs in genetically predisposed individuals secondary to an extra-articular infection, usually of the gastrointestinal or genitourinary tract. Sterile arthritis associated with instillation of intravesical bacillus Calmette-Guérin (iBCG) therapy used for bladder cancer can also be included under ReA based on the pathogenic mechanism. Similar to spondyloarthritis, HLA-B27 positivity is a known contributor to the genetic susceptibility underlying iBCG-associated ReA. Other genetic factors, such as HLA-B39 and HLA-B51, especially in Japanese patients, can also be involved in the pathophysiology of iBCG-associated ReA. The frequencies of ReA- and ReA-related symptoms are slightly different between Japanese and Western studies. Proper understanding of possible complications, their epidemiology and pathogenesis, and their management is important for the rheumatologist when noting symptomatic patients using iBCG. Herein, we will review the most current information on ReA after iBCG therapy.

MRI and Sonography of the Knee in Acute Reactive Arthritis: An Observational Cohort Study.

INTRODUCTION: Reactive arthritis (ReA) is a unique subgroup of spondyloarthritis with acute presentation and tendency to develop chronicity. Magnetic resonance imaging (MRI) has enabled identification of sensitive markers of response to therapy. METHODS: A longitudinal pilot study of acute ReA with knee joint involvement satisfying the Braun's criteria was undertaken. Magnetic resonance imaging of the knee was assessed at baseline, and agreement with ultrasonography was assessed. Clinical details were recorded using a detailed and structured case record form. Patients were followed up, and MRI predictors of transition to chronic arthritis were looked for. RESULTS: In 25 patients with ReA, synovial thickening was the most common feature. Enthesitis was observed on MRI in 20%. Urethritis-related and HLA-B27-positive ReA had higher synovial thickening scores (p = 0.007). Agreement was poor between MRI and ultrasonography (synovial hypertrophy: k = 0.04). On follow-up, 34% (n = 7/21 for >12 months) continued to have active disease. None of the clinical or radiological features were predictive of chronicity. CONCLUSIONS: Posturethritis and B27-positive ReA was more severe than postenteritis ReA and RA on MRI. One third develop chronic disease on follow-up. Magnetic resonance imaging is superior to sonography, although baseline imaging is not predictive of chronicity. The results of this pilot exploratory study argue for larger studies on MRI in ReA.

The Value of Musculoskeletal Ultrasound for Evaluation of Postinfectious Lyme Arthritis.

BACKGROUND: Inflammatory arthritis is the most common late manifestation of untreated Lyme disease in the United States. While antimicrobial therapy is effective in resolving swelling and pain for 90% of patients, many patients have persistent inflammation, termed postinfectious Lyme arthritis (PILA). Current outcome measures for Lyme arthritis have several limitations, as improvement is considered a dichotomous outcome based solely on physical examination. There is growing interest in the use of ultrasonography to better define outcomes in inflammatory arthritis, and this is particularly relevant for conditions such as late Lyme arthritis and PILA, which are monoarticular or oligoarticular. We describe results from a series of 5 patients who underwent ultrasound evaluations leading to a diagnosis of PILA. METHODS: This is a case series describing 5 patients with PILA who were referred for evaluation and treatment of symptomatic joints. RESULTS: Musculoskeletal ultrasound showed significant joint pathology, even in cases with minimal clinical findings. Synovitis, effusions, enthesitis/tendinopathy, and bone erosions were seen and helped confirm the presence of ongoing inflammatory arthritis. CONCLUSIONS: Marked inflammatory change-with synovitis, enthesitis and erosions-can be seen in selected patients with PILA. Systematic sonographic evaluation of patients with PILA is needed to further evaluate pathology and treatment response.