Interleukin (IL)-18 expression in synovial tissue correlates with the severity of joint inflammation and the levels of pro-inflammatory cytokines. However, the role of the IL-18/IL-18 receptor-alpha (Rα) signaling pathway in autoimmune arthritis is unknown. Wild-type (WT) and IL-18Rα knockout (KO) mice were immunized with bovine type II collagen before the onset of arthritis induced by lipopolysaccharide injection. Disease activity was evaluated by semiquantitative scoring and histologic assessment. Serum inflammatory cytokine and anticollagen antibody levels were quantified by an enzyme-linked immunosorbent assay. Joint cytokine and matrix metalloproteinases-3 levels were determined by a quantitative polymerase chain reaction. Splenic suppressors of cytokine signaling (SOCS) were determined by Western blot analysis as indices of systemic immunoresponse. IL-18Rα KO mice showed lower arthritis and histological scores in bone erosion and synovitis due to reductions in the infiltration of CD4+ T cells and F4/80+ cells and decreased serum IL-6, -18, TNF, and IFN-γ levels. The mRNA expression and protein levels of SOCS3 were significantly increased in the IL-18Rα KO mice. By an up-regulation of SOCS, pro-inflammatory cytokines were decreased through the IL-18/IL-18Rα signaling pathway. These results suggest that inhibitors of the IL-18/IL-18Rα signaling pathway could become new therapeutic agents for rheumatoid arthritis.

Osteoporosis is one of the serious adverse effects associated with glucocorticoid therapy. Although bisphosphonates have been used for glucocorticoid-induced osteoporosis (GIO), some patients have shown an inadequate response. In such cases, denosumab or teriparatide are used. However, there is no consensus on which of these two drugs is superior. We prospectively compared denosumab's and teriparatide's effects on the bone mineral density (BMD) in GIO patients with prior bisphosphonate treatment. After receiving oral bisphosphonates for ≥2 years, GIO patients with low T-score BMD (<−2.5) were switched from bisphosphonates to denosumab (n = 20) or daily teriparatide (n = 21). We measured the BMD (lumbar spine, femoral neck, and total hip) in both groups every 6 months for 24 months. At 24 months of treatment, the lumbar spine BMD increased significantly from baseline in both the denosumab and teriparatide groups (baseline vs. denosumab and teriparatide; 5.9 ± 5.6%, P < 0.001 and 7.9 ± 5.4%, P < 0.001). A significant increase in femoral neck BMD from baseline occurred only in the teriparatide group (6.6 ± 10.8%, P < 0.05); denosumab (1.5 ± 5.0%). No significant changes occurred in the total hip BMD from baseline in either group (−0.1 ± 5.6% and 3.3 ± 7.5%, respectively). There was no significant difference between the denosumab and teriparatide groups at 24 months in lumbar spine and femoral neck BMD, but was significantly higher in the teriparatide group at 12 months (P < 0.01 and P < 0.05 in the lumbar spine and femoral neck, respectively). Teriparatide might have some advantages over denosumab and be a good alternative for treating GIO patients with prior bisphosphonate treatment.

Relapsing polychondritis (RP) is a rare autoimmune inflammatory disease characterized by recurrent inflammation and destruction of cartilage. Although auricular chondritis is a characteristic finding in RP, it can be difficult to diagnose in the absence of auricular symptoms. A 64-year-old Japanese male was referred to our hospital with fever and respiratory distress. Contrast-enhanced computed tomography (CT) revealed bronchial wall thickening and we suspected RP; however, he had no auricular symptoms and did not meet the diagnostic McAdam criteria for RP, so we used ¹⁸F-fluorodeoxyglucose positron emission tomography/CT (FDG-PET/CT) to search for other cartilage lesions. This analysis revealed FDG accumulation not only in the bronchial walls, but also in the left auricle. Instead of a bronchial biopsy using a bronchoscope, we performed a biopsy of the left auricular cartilage, which is considered a relatively less invasive site. Even though the auricle was asymptomatic, the pathology results revealed chondritis. He was diagnosed with RP, and his symptoms rapidly improved with corticosteroid therapy. A biopsy of asymptomatic auricular cartilage may be useful in the diagnosis of RP. FDG-PET/CT is a powerful tool for the early diagnosis of RP, identifying inflammatory areas even in the absence of symptoms, and guiding the selection of appropriate biopsy sites.