Loneliness despite social integration: subjective loneliness without social isolation as a risk factor for psychotic-like experiences.

Brucellosis, a zoonotic disease caused by Brucella species, poses a major global health threat, spreading via macrophages to multiple organs and potentially causing multi-systemic complications [, ]. Osteoarticular involvement, such as spondylitis, peripheral arthritis, or sacroiliitis, is a common and debilitating sequelae, especially in mid-to-late disease stages [–]. With an estimated 1.6–2.1 million new cases annually worldwide, brucellosis incidence is alarmingly on the rise [], and its true global burden is likely underestimated, despite being recognized by the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO) as a widespread zoonosis [–]. It also poses a lab infection risk and causes socioeconomic burdens [–]. A critical challenge in managing brucellosis is the non-specific early symptoms, often leading to delayed diagnosis []. The aforementioned osteoarticular manifestations (spondylitis, peripheral arthritis, sacroiliitis), when caused by Brucella, share core features with the broader rheumatological category of Spondyloarthritis (SpA). SpA encompasses a group of systemic inflammatory diseases primarily affecting the axial skeleton, peripheral joints, and entheses. Thus, for the purpose of this study and to reflect its inflammatory nature and specific clinical pattern, we will refer to this constellation of brucellar osteoarticular complications as Brucellar Spondyloarthritis (BrSpA). It’s important to note the distinctions between SpA and BrSpA. SpA is a chronic inflammatory disease marked by inflammatory low back pain, restricted spinal mobility, and peripheral arthritis, treated mainly with NSAIDs for anti-inflammatory and analgesic effects. BrSpA, an infectious spondyloarthritis from Brucella infection in mid-to-late brucellosis, causes joint deformities, chronic pain, disability, and psychological trauma, and is treated primarily with antibiotics [, ]. Despite its prevalence and impact, the transition from uncomplicated brucellosis to BrSpA is not fully understood. Specifically, how clinical and laboratory features evolve during this progression, and what specific factors predispose patients to develop these spondyloarthritis-like manifestations, remain inadequately elucidated. Current clinical studies are limited, hampering the development of targeted preventive and therapeutic strategies for BrSpA. Interestingly, as brucellosis evolves from acute to chronic, patients developing BrSpA may show complex changes. For example, an “improvement” in systemic symptoms or inflammatory markers might paradoxically signal a higher risk of BrSpA. Understanding these shifts is vital for risk assessment. This study, therefore, aims not only to identify conventional risk factors for BrSpA but also to meticulously explore these evolving characteristics in patients progressing through different disease phases. Through a retrospective analysis of 642 cases, comparing patients with established BrSpA, brucellosis without such osteoarticular complications, and healthy controls, we seek to uncover the nuanced patterns and specific risk profiles associated with the development of BrSpA. By elucidating these factors, we intend to provide a more refined framework for early risk stratification, facilitate timely and targeted clinical management, and ultimately improve outcomes for patients with brucellosis at risk of developing these severe osteoarticular complications.