Pachydermodactyly: A Diagnostic Pitfall in Adolescents Referred to Pediatric Rheumatology for Suspected Juvenile Idiopathic Arthritis

Pachydermodactyly (PDD) is a benign, non-inflammatory, non-erosive digital fibromatosis characterized by progressive, asymptomatic, periarticular soft tissue thickening predominantly affecting the proximal interphalangeal (PIP) joints. Additional localizations, including the palm and the distal interphalangeal (DIP) or metacarpophalangeal (MCP) joints, have also been reported. The etiology of PDD is multifactorial, encompassing idiopathic, trauma-induced, genetic, and behavioral factors. Objective: The aim of this report is to describe the clinical, imaging, and laboratory features of pachydermodactyly in two male adolescents initially referred to a pediatric rheumatology service for suspected juvenile idiopathic arthritis (JIA), highlighting the diagnostic pitfalls and differentiation criteria from inflammatory arthritis. In addition, a narrative review of cases published from 1975 to 2025 is presented to contextualize our findings within the broader literature. Results: Two male adolescents (aged 13 years and 5 months and 16 years) presented with progressive, painless periarticular soft tissue swelling of the PIP joints, initially raising suspicion for JIA. Comprehensive evaluation identified characteristic features of PDD in both patients, with complete absence of inflammatory markers, synovitis, or osseous changes. Case 1 was classified as mono-PDD and Case 2 as classic, trauma-associated PDD with atypical perilesional hypopigmentation, requiring MRI for definitive exclusion of infiltrative pathology. A narrative review of 15 representative published cases from 2014 to 2025 is presented, demonstrating persistent underdiagnosis and consistent misclassification as JIA across multiple clinical settings and geographic regions. Conclusions: PDD should be considered in the differential diagnosis of any adolescent presenting with painless digital swelling. Its recognition as a benign, non-inflammatory entity is essential to prevent unnecessary diagnostic procedures and immunosuppressive therapy. Clinical awareness and multidisciplinary assessment remain the cornerstones of accurate diagnosis and appropriate management.