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.

Leniolisib, a selective phosphoinositide 3-kinase δ (PI3Kδ) inhibitor, is approved in several countries for the treatment of activated PI3Kδ syndrome (APDS) in patients 12 years of age and older. We report the first successful compassionate use of leniolisib in another inborn error of immunity, protein kinase C δ deficiency. In addition to infectious complications, the 14-year-old patient experienced lymphoproliferation in the form of splenomegaly, lymphadenopathy, and thymic hyperplasia; trilineage cytopenia; multiple forms of autoimmunity; and interstitial lung disease. Decision to initiate treatment with leniolisib was based on multiorgan-disease progression, lack of therapeutic alternatives, molecular evidence, overlap with APDS manifestations, and mammalian target of rapamycin hyperactivity. We observed improvement in lymphoproliferation, cytopenias, hepatic cytolysis, skin manifestations, pulmonary function, favorable changes in immunophenotypes, and no known drug-related adverse events. This experience supports expanding Leniolisib’s potential indications to appropriately selected patients and conditions. Broader repurposing strategies for targeted therapies in diseases involving dysregulated PI3K signaling should be systematically evaluated in clinical trials.

Immunoglobulin G4-related disease (IgG4-RD) is an immune-mediated fibroinflammatory disorder primarily affecting adults. The disease in pediatric age is unusual and preferentially affects adolescents. In contrast to adults, who commonly exhibit the involvement of multiple organs simultaneously or sequentially over time, young patients tend to present with a localized disease, typically affecting the orbits. Proptosis, ptosis, diplopia, and restricted eye movement may be observed in these patients. Symptoms are proteiform, and the disease is chronic and indolent with a relapsing–remitting course. Diagnostic criteria have been developed for adults, which may not fully capture the pediatric disease phenotype. If untreated or poorly managed, IgG4-RD can lead to progressive fibrosis and scarring of affected organs, potentially causing irreversible damage. We conducted a narrative review using the IMRAD approach, presenting a nonsystematic analysis of the literature on pediatric IgG4-RD. Original papers, case reports/series, and relevant reviews in English were selected from PubMed, EMBASE, and Web of Science up to January 2024. Keywords included “IgG4-Related Disease” and “pediatric” and, additionally, we presented two original pediatric cases. Our purpose is to offer an overview of IgG4-RD manifestations, and challenges in diagnosing and managing this rare condition in children.

Background: Scurvy is an uncommon and often underrecognized disease. However, conditions associated with a restrictive and/or selective diet and inadequate absorption still pose a high risk for developing vitamin C deficiency. Musculoskeletal symptoms are among the most characteristic manifestations of scurvy, often requiring radiological investigations. Objective: This study aims to describe the radiological signs of scurvy on pelvic magnetic resonance imaging (MRI) in children presenting with musculoskeletal symptoms and to highlight features that may help differentiate it from other conditions with similar presentations. Methods: We conducted a retrospective study including children admitted for musculoskeletal symptoms requiring a pelvic MRI and who were subsequently diagnosed with scurvy. Demographic, clinical, laboratory, and radiological data were extracted from electronic medical records. Results: We identified ten patients with a median age at disease onset of 45 months (range 17–133 months) admitted between 2016 and 2022. All ten patients included in the study were male. All had at least one of the following symptoms: limping, pain in the lower limbs, or refusal to walk, in addition to gum bleeding (7/10), hypertrophic gums (5/10), purpura (3/10), irritability (3/10), and fever (2/10). In all patients, pelvic MRI showed a bilateral, patchy, abnormal, water-like signal intensity pattern in the sacroiliac area. Sacroiliitis was detected in three children and hip effusion in another child. Seven out of these ten patients had a previous pelvis X-ray that was negative. Conclusions: In scurvy, the pelvis is often prematurely affected, with bone marrow accumulating water and joints showing inflammatory changes, particularly at the hips and sacroiliac joints. Due to its ability to assess soft tissues and its high sensitivity to water content, MRI is the ideal imaging tool to assess these changes. In contrast, plain radiography is less sensitive and specific and may be uninformative in the early stages of the disease.

Purpose: The purpose of this study was to evaluate the feasibility of magnetic resonance imaging (MRI)-based radiomics derived from routine T2-weighted imaging for initial risk stratification in pediatric neuroblastoma (NB) and to explore its potential role as a noninvasive adjunct to established clinical and molecular classification systems. Methods: In this retrospective, single-center pilot study, 45 children with newly diagnosed NB (2015–2024) were analyzed. Primary tumors were manually segmented on baseline axial T2-weighted MRI. A total of 107 Image Biomarker Standardization Initiative (IBSI)-compliant radiomic features were extracted. Supervised machine learning classifiers (Random Forest, XGBoost) and dimensionality reduction approaches (principal component analysis [PCA], linear discriminant analysis [LDA]) combined with K-means clustering were evaluated. Model performance was assessed using stratified cross-validation and an independent test set. Reporting adhered to the Checklist for Evaluation of Radiomics Research (CLEAR). Results: Fifteen patients (33%) were classified as high-risk (HR) and 30 (67%) as non-high-risk (NHR) according to International Neuroblastoma Risk Group (INRG) criteria. The highest classification performance was achieved using LDA followed by K-means clustering, with a test accuracy of 77.8%, sensitivity of 64.7%, and specificity of 85.7%. Radiomic classification agreed with conventional risk stratification in 77.8% of cases. The analysis relied exclusively on T2-weighted imaging, supporting workflow feasibility without requiring contrast administration or advanced MRI sequences. Conclusions: In this single-center pilot study, T2-weighted MRI radiomics demonstrated feasibility for noninvasive initial risk stratification in pediatric NB. Although limited by sample size and the lack of external validation, these findings support further multicenter investigations of radiomics as an adjunctive imaging biomarker during early diagnostic evaluation.