Unmasking JIA mimics: skeletal dysplasias in pediatric rheumatology

This study aims to delineate the clinical, demographic, and molecular characteristics of skeletal dysplasias (SD) referred to a pediatric rheumatology clinic and to identify diagnostic indicators for differentiating these genetic conditions from inflammatory mimics, such as juvenile idiopathic arthritis (JIA), according to the 2023 International Skeletal Dysplasia Society (ISDS) classification. This study analyzed the demographic, clinical, and diagnostic characteristics of patients diagnosed with SD who were referred to the pediatric rheumatology clinic at Ümraniye Training and Research Hospital between 2016 and 2025. Molecular diagnosis was confirmed using next-generation sequencing (NGS) with a targeted SD gene panel. Among the 36 patients included in the study, 21 were female and 15 were male. The median age at symptom onset was 8.3 years (range: 2.1-17.8), while the median age at genetic diagnosis was 11 years (range: 1.9-17.8). According to the 2023 ISDS classification, the most common diagnoses were genetic inflammatory or rheumatoid-like osteoarthropathies, spondylometaphyseal dysplasias (SMD), and type 11 collagen disorders. The most common clinical manifestations were arthralgia (n = 31, 86%), joint swelling (n = 30, 83%), joint deformities (n = 21, 58%), and pachydermodactyly (n = 18, 50%). The most frequent physical examination finding was restricted joint mobility (n = 16, 44%).

This study highlights the importance of distinguishing genetic disorders mimicking rheumatologic diseases in differential diagnosis and aims to increase awareness of these genetic conditions among clinicians.

• Skeletal dysplasias are often misdiagnosed as juvenile idiopathic arthritis due to overlapping musculoskeletal symptoms and diagnostic challenges. • Misdiagnosis leads to diagnostic delays, unnecessary immunosuppressive treatments, and significant psychosocial burdens for pediatric patients.

• This research represents one of the most contemporary studies to classify and analyze these conditions according to the updated Nosology of Genetic Skeletal Disorders: 2023 revision.. • This represents the largest cohort to date in a pediatric rheumatology setting, identifying key clinical and laboratory clues for accurate differentiation.