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Decision Tree Analysis as a Preliminary Evidence-Based Tool for Identifying the Syndrome of Undifferentiated Recurrent Fever in Children Compared With Hereditary Recurrent Fevers and Periodic Fever, Aphthosis, Pharyngitis, and Adenitis Syndrome.

To develop evidence-based criteria to classify patients with syndrome of undifferentiated recurrent fevers (SURF). One hundred twelve patients with SURF observed in a single tertiary referral center were analyzed. Patients with genetically confirmed hereditary recurrent fever (HRF) or with periodic fever, aphthosis, pharyngitis, and adenitis (PFAPA) syndrome already analyzed for the Eurofever classification criteria were used as disease controls. A decision tree approach was tested by randomly splitting the available data in a training set and in an internal test set. An alternative model using a classical regression model was also analyzed. An external validation for both approaches was performed on 123 patients recruited from four other centers. The decision tree model integrating clinical and genetic data identified 91% of patients with SURF. A decision tree model based solely on clinical variables identified up to 88% of patients with SURF. The logistic regression model including genetic tests exhibited an overall accuracy of 89.2% (95% confidence interval [CI] 81.1-94.7). In contrast, the logistic regression model exclusively based on clinical manifestations displayed an overall accuracy of 66.7% (95% CI 56.1-76.1). When the classification criteria including genetic tests were applied to the external validation cohort, the model demonstrated a strong discriminative power, with areas under the receiver operating characteristic curve of 96.3% using the decision tree model and 88.0% with the logistic regression model. The study shows the possibility of achieving evidence-based criteria that can classify SURF at least with respect to the main HRF and PFAPA syndrome and may be considered as a preliminary tool for the enrollment of more homogeneous cohorts of patients in future studies.

Predictive factors for therapeutic response and cluster analysis in syndrome of undifferentiated recurrent fever (SURF).

Syndrome of undifferentiated recurrent fever (SURF) refers to a group of recurrent fevers without a clear monogenic cause. Clinical spectrum, treatment response predictors and management strategies remain unclear. This study aims to longitudinally analyse a homogeneously selected cohort of 101 SURF patients, to identify factors associated with colchicine resistance and to evaluate the efficacy of interleukin-1 (IL-1) inhibitors. Patients were enrolled in the Eurofever Registry, carefully excluding those with periodic fever, aphthous stomatitis, pharyngitis and cervical adenitis (PFAPA); familial Mediterranean fever and other known monogenic recurrent fevers. Demographic, clinical and treatment data were analysed to identify predictors of colchicine resistance and define subgroups through cluster analysis. Common symptoms included fever, arthralgia, abdominal pain and myalgia, with PFAPA-like features (lymphadenopathy, tonsillitis, oral aphthae) observed in one-third of cases, sporadically. Colchicine efficacy, assessed in 77 patients, revealed complete response in the majority of patients (61%). Univariable analysis identified PFAPA-like features, including aphthous stomatitis (p=0.001), cervical lymphadenopathy (p=0.012) and exudative tonsillitis (p=0.004), as associated with colchicine resistance. Multivariable analysis confirmed aphthous stomatitis as an independent predictor of resistance (p=0.014). Tonsillectomy was ineffective. IL-1 inhibitors (anakinra, canakinumab) were beneficial in refractory cases. Cluster analysis revealed three distinct subgroups with varying symptoms and colchicine responses. These findings provide new insights into SURF, identifying predictors of colchicine resistance and supporting the efficacy of IL-1 blockade. Cluster analysis suggests the heterogeneity within SURF, reinforcing the need for refined diagnostic criteria and personalised treatment strategies.

Unravelling the clinical heterogeneity of undefined recurrent fever over time in the European registries on Autoinflammation.

Systemic autoinflammatory disorders (SAIDs) represent a growing spectrum of diseases characterized by dysregulation of the innate immune system. The most common pediatric autoinflammatory fever syndrome, Periodic Fever, Aphthous Stomatitis, Pharyngitis, Adenitis (PFAPA), has well defined clinical diagnostic criteria, but there is a subset of patients who do not meet these criteria and are classified as undefined autoinflammatory diseases (uAID). This project, endorsed by PRES, supported by the EMERGE fellowship program, aimed to analyze the evolution of symptoms in recurrent fevers without molecular diagnosis in the context of undifferentiated AIDs, focusing on PFAPA and syndrome of undifferentiated recurrent fever (SURF), using data from European AID registries. Data of patients with PFAPA, SURF and uSAID were collected from 3 registries including detailed epidemiological, demographic and clinical data, results of the genetic testing and additional laboratory investigations with retrospective application of the modified Marshall and PRINTO/Eurofever classification criteria on the cohort of PFAPA patients and preliminary SURF criteria on uSAID/SURF patients. Clinical presentation of PFAPA is variable and some patients did not fit the conventional PFAPA criteria and exhibit different symptoms. Some patients did not meet the criteria for either PFAPA or SURF, highlighting the heterogeneity within these groups. The study also explored potential overlaps between PFAPA and SURF/uAID, revealing that some patients exhibited symptoms characteristic of both conditions, emphasizing the need for more precise classification criteria. Patients with recurrent fevers without molecular diagnoses represent a clinically heterogeneous group. Improved classification criteria are needed for both PFAPA and SURF/uAID to accurately identify and manage these patients, ultimately improving clinical outcomes.

Pyrin Inflammasome Activation Defines Colchicine-Responsive SURF Patients from FMF and Other Recurrent Fevers.

Syndrome of undifferentiated recurrent fever (SURF) is characterized by recurrent fevers, a lack of confirmed molecular diagnosis, and a complete or partial response to colchicine. Despite the clinical similarities to familial Mediterranean fever (FMF), the underlying inflammatory mechanisms of SURF are not yet understood. We here analyzed the in vitro activation of the pyrin inflammasome in a cohort of SURF patients compared to FMF and PFAPA patients. Peripheral blood mononuclear cells (PBMC) were collected from SURF (both colchicine-treated and untreated), FMF, PFAPA patients, and healthy donors. PBMC were stimulated ex vivo with Clostridium difficile toxin A (TcdA) and a PKC inhibitor (UCN-01), in the presence or absence of colchicine. The assembly of the pyrin inflammasome was evaluated by measuring the presence of apoptosis-associated Speck-like protein containing caspase recruitment domain (ASC) specks in monocytes using flow cytometry. IL-1β secretion was quantified using an ELISA assay. No differences in TcdA-induced activation of pyrin inflammasome were observed among FMF, PFAPA, and healthy donors. Untreated SURF patients showed a reduced response to TcdA, which was normalized after colchicine treatment. In contrast to FMF, SURF patients, similar to PFAPA patients and healthy donors, did not exhibit pyrin inflammasome activation in response to UCN-01-mediated pyrin dephosphorylation. These data demonstrate that in vitro functional analysis of pyrin inflammasome activation can differentiate SURF from FMF and PFAPA patients, suggesting the involvement of the pyrin inflammasome in the pathophysiology of SURF.

Clinical characterization, long-term follow-up, and response to treatment of patients with syndrome of undifferentiated recurrent fever (SURF).

To describe a homogeneous group of patients with undifferentiated recurrent fevers followed-up in a tertiary referral center for systemic autoinflammatory diseases (SAIDs). Patients with undifferentiated recurrent fevers seen at our Center from 2008 to 2021 and followed-up for at least one year were included in a retrospective study. Monogenic recurrent fevers, patients carrying variants of unknown origin and PFAPA (Periodic Fever, Aphthous Stomatitis, Pharyngitis, Adenitis) syndrome were excluded. Fifty patients (34 male, 16 female) were included in the study. The median age at onset was 3 years, and the median follow-up was 3.3 years. At baseline, arthralgia (70%) and abdominal pain (65%) were the most frequent manifestations. NSAIDs or steroids on demand had a variable and transient effect. Tonsillectomy was ineffective in the 10 patients (20%) that underwent surgery. Forty-eight patients (96%) were treated with colchicine. A complete response (absence of fever) was achieved in 31 patients (64.6%). Nine patients (18%) showed a partial response, with a median reduction of fever episodes per year of 72%. Nine patients (16.7%) were considered resistant to colchicine. The presence of generalized lymphadenopathy and, to a lesser extent, exudative tonsillitis was associated with a lack of response to colchicine. We describe the largest series of patients with syndrome of undifferentiated recurrent fever (SURF) reported in the literature so far. SURF should be considered as a distinct clinical entity in the context of multifactorial autoinflammatory diseases.

Syndrome of Undifferentiated Recurrent Fever (SURF): An Emerging Group of Autoinflammatory Recurrent Fevers.

Syndrome of undifferentiated recurrent fever (SURF) is a heterogeneous group of autoinflammatory diseases (AID) characterized by self-limiting episodes of systemic inflammation without a confirmed molecular diagnosis, not fulfilling the criteria for periodic fever, aphthous stomatitis, pharyngitis and adenopathy (PFAPA) syndrome. In this review, we focused on the studies enrolling patients suspected of AID and genotyped them with next generation sequencing technologies in order to describe the clinical manifestations and treatment response of published cohorts of patients with SURF. We also propose a preliminary set of indications for the clinical suspicion of SURF that could help in everyday clinical practice.

Next generation sequencing panel in undifferentiated autoinflammatory diseases identifies patients with colchicine-responder recurrent fevers.

The number of innate immune system disorders classified as systemic autoinflammatory diseases (SAID) has increased in recent years. More than 70% of patients with clinical manifestations of SAID did not receive a molecular diagnosis, thus being classed as so-called undifferentiated or undefined SAID (uSAID). The aim of the present study was to evaluate a next-generation sequencing (NGS)-based clinically oriented protocol in patients with uSAID. We designed a NGS panel that included 41 genes clustered in seven subpanels. Patients with uSAID were classified into different groups according to their clinical features and sequenced for the coding portions of the 41 genes. Fifty patients were enrolled in the study. Thirty-four patients (72%) displayed recurrent fevers not consistent with a PFAPA phenotype. Sixteen patients displayed a chronic inflammatory disease course. A total of 100 gene variants were found (mean 2 per patient; range 0-6), a quarter of which affected suspected genes. Mutations with a definitive diagnostic impact were detected in two patients. Patients with genetically negative recurrent fevers displayed a prevalent gastrointestinal, skin and articular involvement. Patients responded to steroids on demands (94%) and colchicine, with a response rate of 78%. Even with a low molecular diagnostic rate, a NGS-based approach is able to provide a final diagnosis in a proportion of uSAID patients with evident cost-effectiveness. It also allows the identification of a subgroup of genetically negative patients with recurrent fever responding to steroid on demand and colchicine.

Early onset PFAPA-like syndrome in a child with microduplication of the 7q11.23.