Rheumatoid arthritis (RA) is characterized by extra‐articular involvement including lung disease, yet the mechanisms linking the two conditions are poorly understood. The collagen‐induced arthritis (CIA) model was combined with the organic dust extract (ODE) airway inflammatory model to assess bone/joint–lung inflammatory outcomes. DBA/1J mice were intranasally treated with saline or ODE daily for 5 weeks. CIA was induced on days 1 and 21. Treatment groups included sham (saline injection/saline inhalation), CIA (CIA/saline), ODE (saline/ODE), and CIA +  ODE (CIA/ODE). Arthritis inflammatory scores, bones, bronchoalveolar lavage fluid, lung tissues, and serum were assessed. In DBA/1J male mice, arthritis was increased in CIA +  ODE >  CIA >  ODE versus sham. Micro‐computed tomography (µCT) demonstrated that loss of BMD and volume and deterioration of bone microarchitecture was greatest in CIA +  ODE. However, ODE‐induced airway neutrophil influx and inflammatory cytokine/chemokine levels in lavage fluids were increased in ODE >  CIA +  ODE versus sham. Activated lung CD11c+CD11b+ macrophages were increased in ODE >  CIA +  ODE >  CIA pattern, whereas lung hyaluronan, fibronectin, and amphiregulin levels were greatest in CIA +  ODE. Serum autoantibody and inflammatory marker concentrations varied among experimental groups. Compared with male mice, female mice showed less articular and pulmonary disease. The interaction of inhalation‐induced airway inflammation and arthritis induction resulted in compartmentalized responses with the greatest degree of arthritis and bone loss in male mice with combined exposures. Data also support suppression of the lung inflammatory response, but increases in extracellular matrix protein deposition/interstitial disease in the setting of arthritis. This coexposure model could be exploited to better understand and treat RA–lung disease. © 2019 American Society for Bone and Mineral Research.

An agriculture organic dust extract inhalation animal model has recently linked lung injury-induced inflammation to systemic bone loss. This process is dependent upon lipopolysaccharide and the toll-like receptor 4 (TLR4) signaling pathway. Downstream systemic interleukin-6 is a key mediator that subsequently activates osteoclastogenesis. Age is a host factor that impacted bone disease with younger mice demonstrating increased susceptibility to bone loss following inhalant exposures as compared to older mice. Supplemental dietary vitamin D was shown to prevent organic dust-induced bone loss, but not lung disease, in animals. Recent animal studies provide new mechanistic insight into the lung-bone inflammatory axis. Host factors, diet, and lipopolysaccharide/TLR4 signaling pathways play a significant role in explaining how inhalant organic dust exposures impact bone health. These investigations might lead to specific targeted therapeutic approaches.

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Central pontine myelinolysis (CPM) is classically attributed to overly rapid correction of profound hyponatremia. However, there are case reports of this disease in the setting of normal serum sodium or minimal hyponatremia. These cases have been hypothesized to be secondary to other metabolic disturbances such as hyperglycemia or hypophosphatemia. Eunatremic CPM has also been described in patients with advanced acquired immune deficiency syndrome (AIDS). The mortality risk in this special population is significantly higher than those with hyponatremia-associated CPM, but the mechanisms are unclear. We discuss a case of a man with AIDS who developed CPM with minimal hyponatremia and no other metabolic disturbances. Common variables within this population, such as hypoalbuminemia and lymphoma, are discussed as potential factors contributing to the pathophysiology. Reporting these atypical cases is crucial to our understanding of how to prevent future cases.