Purpose or Case Report: Sterile pyogenic arthritis, pyoderma gangrenosum, and acne (PAPA syndrome) is a rare autosomal dominant inherited entity due to a missense mutation in the proline serine threonine phosphatase-interacting protein 1 (PSTPIP1/CD2BP1) gene, characterized by typical recurrent episodes of sterile pyogenic arthritis, either spontaneous or following a trauma, and skin manifestations characterized by pyoderma gangrenosum and acne. The articular manifestation is seen in the first decade of life, where most of the initial episodes are treated as septic arthritis. Cutaneous manifestations appear in early adulthood. Although uncommon, the potential therapeutic and clinical implications due to the rapidly destructive nature of PAPA syndrome warrant a prompt diagnosis. We present two unrelated pediatric patients from different institutions with genetically confirmed PAPA syndrome. The purpose of this study was to illustrate the musculoskeletal radiologic spectrum of findings of PAPA syndrome, and to discuss the differential diagnostic entities commonly seen in children. A second objective was to review the clinical and laboratory findings that allow diagnosis of PAPA syndrome
Methods & Materials:
Patients’ consent were obtained. We reviewed the imaging features of PAPA syndrome in different imaging modalities including plain radiograph, ultrasound, and magnetic resonance imaging, and we included representative cases of more common musculoskeletal diagnostic entities that present with similar imaging and clinical features in children
Results: Many of the imaging features seen in PAPA syndrome overlap with other clinical conditions including septic arthritis, osteomyelitis and juvenile idiopathic arthritis, including joint effusion, synovial thickening and extensive soft tissue swelling
Conclusions: PAPA syndrome would not be suspected initially based on imaging appearance alone, but should be considered in cases of recurrent septic arthritis or in those demonstrating skin manifestations. Radiologists familiarization with the syndrome may allow them to recognize the condition earlier in its course