Objective: Our objective was to develop and validate cutoff values in the systemic Juvenile Arthritis Disease Activity Score 10 (sJADAS10) that distinguish the states of inactive disease (ID), minimal disease activity (MDA), moderate disease activity (MoDA), and high disease activity (HDA) in children with systemic juvenile idiopathic arthritis, based on subjective disease state assessment by the treating pediatric rheumatologist.Methods: The cutoff definition cohort was composed of 400 patients enrolled at 30 pediatric rheumatology centers in 11 countries. Using the subjective physician rating as an external criterion, six methods were applied to identify the cutoffs: mapping, calculation of percentiles of cumulative score distribution, the Youden index, 90% specificity, maximum agreement, and receiver operating characteristic curve analysis. Sixty percent of the patients were assigned to the definition cohort, and 40% were assigned to the validation cohort. Cutoff validation was conducted by assessing discriminative ability.Results: The sJADAS10 cutoffs that separated ID from MDA, MDA from MoDA, and MoDA from HDA were ≤2.9, ≤10, and >20.6, respectively. The cutoffs discriminated strongly among different levels of pain, between patients with and without morning stiffness, and among patients whose parents judged their disease status as remission or persistent activity or flare or were satisfied or not satisfied with current illness outcome.Conclusion: The sJADAS cutoffs revealed good metrologic properties in both definition and validation cohorts and are therefore suitable for use in clinical trials and routine practice.

Pyomyositis (PM) is an infrequent but increasing bacterial infection of the skeletal muscle, with muscles of the pelvis and thigh frequently involved. The diagnosis is often challenging, especially when a deep muscle is affected. We present a single-center pediatric cohort affected by pelvic PM. A retrospective analysis was performed, including children admitted to Meyer Children’s Hospital between 2010 and 2020. Demographic, anamnestic, clinical, laboratory, radiological and management data were collected. Forty-seven patients (range 8 days–16.5 years, 66% males) were selected. Pain (64%), functional limitations (40%) and fever (38%) were the most common presenting symptoms; 11% developed sepsis. The median time to reach the diagnosis was 5 days (IQR 3–9). Staphylococcus aureus was the most common organism (30%), Methicillin-Resistant S aureus (MRSA) in 14%. PM was associated with osteomyelitis (17%), arthritis (19%) or both (45%). The infection was multifocal in 87% of children and determined abscesses in 44% (40% multiple). Pelvic MRI scan, including diffusion-weighted imaging (DWI), always showed abnormalities when performed. Clinical and laboratory findings in pelvic PM are unspecific, especially in infancy. Nevertheless, the infection may be severe, and the suspicion should be higher. MRI is the most useful radiological technique, and DWI sequence could reveal insidious infections.

This narrative review aims to report the main clinical manifestations, therapeutic strategies, outcomes, and complications of acute SARS-CoV-2 infection in childhood and to summarize the data relating the SARS-CoV-2 vaccination efficacy and safety in pediatric age. SARS-CoV-2 infection mostly occurs asymptomatically in the pediatric population, while multisystem inflammatory syndrome in children (MIS-C) represents the most severe coronavirus disease 2019 (COVID-19)-related illness, a life-threatening event with a high morbidity rate. After the development of SARS-CoV-2 vaccines and their subsequent approval in children, the rate of infection as well as the number of its related complications have shown a drastic decrease. Fully vaccinated children are protected from the risk of developing a severe disease and a similar protective role has been observed in the reduction of complications, in particular MIS-C. However, long-lasting immunity has not been demonstrated, booster doses have been required, and reinfection has been observed. With regards to vaccine safety, adverse events were generally mild to moderate in all age groups: local adverse events were the most commonly reported. Nevertheless, a potential association between SARS-CoV-2 vaccine and the subsequent development of inflammatory manifestations has been suggested. Myocarditis has rarely been observed following vaccination; it appeared to be more frequent among adolescent males with a mild clinical course leading to a complete recovery. SARS-CoV-2 vaccine-related MIS-C cases have been described, although a univocal definition and an exact time interval with respect to vaccination has not been reported, thus not establishing a direct causal link. Current evidence about COVID-19 vaccination in children and adolescents suggest that benefits outweigh potential risks. Long-term data collection of the post-authorization safety surveillance programs will better define the real incidence of SARS-CoV-2 vaccine-related complications in the pediatric population.

Bartonella henselae is an unusual and rarely suspected osteomyelitis etiologic agent. We present a case of low back‐pain in a 10‐year‐old female which lead to a challenging diagnostic work‐up due to subtle imaging findings. The diagnosis was Bartonella henselae vertebral osteomyelitis mimicking bone tumor.

Valerio Maniscalco, Ilaria Pagnini, Edoardo Marrani, Ilaria Maccora, Sarah Abu Rumeileh, Maria Vincenza Mastrolia, Gabriele Simonini; Comment on: Achieving inac

Immune dysregulation is being increasingly recognized as a prominent feature of a wide range inborn errors of immunity (IEIs) with different molecular backgrounds. Among the manifestations of immune dysregulation, inflammatory arthritis has emerged as an important yet underrecognized complication that may occur across multiple IEI categories, including humoral immunodeficiencies (such as X-linked agammaglobulinemia, hyper-IgM syndrome, common variable immunodeficiency, and others), complement deficiencies, disorders of immune dysregulation (STAT3 gain of function mutation, CTLA4 and LRBA haploinsufficiency), and combined immunodeficiencies. In some patients, arthritis may represent the first or predominant clinical manifestation, resulting in a diagnostic challenge in the rheumatologic setting. The pathogenesis of arthritis in IEIs reflects different immunological mechanisms, including the defective clearance of immune complexes, dysregulated B- and T-cell responses, impaired regulatory T-cell function, and aberrant cytokine signaling. Clinically, IEI-associated arthritis may mimic classical rheumatologic conditions such as juvenile idiopathic arthritis, rheumatoid arthritis, or other connective tissue diseases, although distinctive immunological and histopathological features are often present. Recognizing arthritis as a potential manifestation of IEIs has important clinical implications. The presence of specific “red flags”, including treatment refractoriness, recurrent infections, or additional signs of immune dysregulation (other autoimmune diseases, atopy, lymphoproliferation, enteropathy), should prompt targeted immunological evaluation. While management often relies on conventional immunosuppressive therapies, advances in the molecular characterization of IEIs are increasingly enabling the use of targeted treatments directed at the underlying pathogenic mechanisms. This paper provides an overview of the current knowledge of arthritis associated with IEIs, highlighting diagnostic challenges, underlying immunopathogenic mechanisms, and emerging therapeutic perspectives.