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In this insightful session, Prof. Rolando Cimaz, head of the Pediatric Rheumatology Unit at Meyer Children’s Hospital in Florence, addresses the challenge of distinguishing juvenile idiopathic arthritis (JIA) from inherited metabolic and skeletal disorders. Drawing from detailed case studies and imaging, he explains how metabolic diseases such as mucopolysaccharidoses (MPS) can mimic rheumatologic conditions, often resulting in misdiagnosis and delayed treatment.
Prof. Cimaz begins by outlining that JIA is a diagnosis of exclusion. Many conditions can present with joint symptoms in childhood, and early differentiation is critical. Through various cases, he demonstrates how inherited disorders such as Stickler syndrome, progressive pseudorheumatoid dysplasia (PPRD), and mucopolysaccharidoses share features with inflammatory arthritis—including joint stiffness, pain, and functional limitations—but lack classic inflammatory signs like joint swelling and elevated inflammatory markers.
He presents a case of Stickler syndrome, where myopia and retinal detachment preceded joint stiffness and hypermobility. He emphasizes the significance of extra-articular features—such as hearing loss, facial dysmorphism, and ocular abnormalities—in raising suspicion for genetic syndromes rather than JIA. Another case, involving a boy with progressive joint contractures and limited mobility, led to a diagnosis of PPRD, a genetic bone dysplasia identifiable through characteristic X-ray findings and confirmed by WISP3 gene mutation.
A major focus is placed on mucopolysaccharidoses, particularly MPS I and MPS VI, which can present in childhood with joint stiffness, contractures, and claw-hand deformities—often without overt inflammation. Prof. Cimaz stresses that attenuated forms of MPS may lack the classic facial or systemic features, further complicating diagnosis. He highlights bilateral carpal tunnel syndrome in children as a red flag that should prompt investigation for storage disorders.
Diagnostic clues discussed include normal inflammatory markers, absence of synovial effusion despite joint limitation, and characteristic skeletal abnormalities visible on imaging. He urges clinicians to consider urinary glycosaminoglycan testing and refer to specialized metabolic centers when MPS is suspected. Early diagnosis is essential, as treatments such as enzyme replacement therapy and hematopoietic stem cell transplantation can significantly improve outcomes.
Prof. Cimaz concludes with key advice: pediatric rheumatologists and generalists should think beyond inflammatory arthritis when faced with unexplained joint symptoms in children. A high index of suspicion, thorough physical examination, and collaboration with metabolic specialists are essential to avoid years of diagnostic delay.