Teresa Giani

Juvenile idiopathic arthritis (JIA) is the most common chronic rheumatic condition in childhood. The disease etiology remains largely unknown; however, a key role in JIA pathogenesis is surely mediated by T cells. T‐lymphocytes activity is controlled via signals, known as immune checkpoints. Delivering an inhibitory signal or blocking a stimulatory signal to achieve immune suppression is critical in autoimmune diseases. However, the role of immune checkpoints in chronic inflammation and autoimmunity must still be deciphered. In this study, we investigated at the single‐cell level the feature of T cells in JIA chronic inflammation, both at the transcriptome level via single‐cell RNA sequencing and at the protein level by flow cytometry. We found that despite the heterogeneity in the composition of synovial CD4 + and CD8 + T cells, those characterized by PD‐1 expression were clonally expanded tissue‐resident memory (Trm)‐like cells and displayed the highest proinflammatory capacity, suggesting their active contribution in sustaining chronic inflammation in situ. Our data support the concept that novel therapeutic strategies targeting PD‐1 may be effective in the treatment of JIA. With this approach, it may become possible to target overactive T cells regardless of their cytokine production profile.

Background Chronic recurrent multifocal osteomyelitis (CRMO) is a bone inflammatory disorder characterized by osteolytic, usually multiple, symmetric lesions. Diagnosis is one of exclusion, and no standardized therapies are available. Presumed deregulation of the interleukin (IL)‐1β axis, as observed in 2 monogenic autoinflammatory conditions such as Majeed syndrome (LPIN2 mutations) and deficiency of IL‐1 receptor antagonist (IL1RN mutations) with CRMO‐like bone involvement, suggests the blockade of IL‐1 as potentially useful also in this condition, even if scarce data are available. Case presentation We report the case of a 13‐year‐old girl affected by a multidrug‐resistant and pyoderma gangrenosum‐complicated CRMO treated with canakinumab, a human monoclonal antibody targeting IL‐1β. Conclusion In this young patient pyoderma gangrenosum and CRMO showed a rapid and satisfactory response to canakinumab, although over time a decreased efficacy in controlling bone disease was observed.