Osteoporosis in autoimmune and inflammatory diseases: prevalence, risks, and management

Q. What does current epidemiological evidence tell us about osteoporosis prevalence and fracture risk in autoimmune and inflammatory diseases?

Current epidemiological evidence indicates that osteoporosis represents a highly prevalent comorbidity across the spectrum of rheumatologic and autoimmune diseases. In the context of progressively aging patient populations, a substantial increase in the absolute burden of individuals affected by both inflammatory disease and concomitant osteoporosis is to be anticipated.

Across a range of conditions, including RA, SpA, SLE, and SSc, a consistently elevated prevalence of osteoporosis has been demonstrated in comparison to the general population. Notably, in SLE the risk of developing osteoporosis is increased by approximately 2- to 2.5-fold, while patients with vasculitis exhibit an almost 3-fold increased risk.

Crucially, this increased prevalence translates into a significantly heightened fracture risk. This elevated risk is not solely attributable to reductions in bone mineral density (BMD), but rather reflects a multifactorial impairment of skeletal integrity, encompassing alterations in bone microarchitecture, chronic systemic inflammation and disease-associated reductions in physical mobility.

Taken together, these findings underscore that osteoporosis should be regarded not merely as a secondary condition, but as a central and clinically relevant comorbidity in patients with chronic inflammatory diseases.

Q. Which diseases carry the highest osteoporosis risk, and what key mechanisms drive bone loss in these populations?

The highest risk of osteoporosis is observed in patients with chronic inflammatory rheumatologic diseases, most notably RA, SpA, SLE, SSc and systemic vasculitides. The underlying mechanisms of bone loss in these conditions are inherently multifactorial, yet converge on several shared pathophysiological pathways:

• Chronic inflammation with increased cytokines, such as tumour necrosis factor alpha (TNF-α), interleukin-1 (IL-1) and interleukin-6 (IL-6);
• Upregulation of RANKL, promoting osteoclast differentiation and bone resorption;
• Inhibition of the Wnt/β-catenin pathway, impairing osteoblast function via mediators like Dickkopf-1 (Dkk-1) and sclerostin;
• Autoantibodies, such as anti-citrullinated protein antibodies (anti-CCP) in RA, directly stimulating osteoclastogenesis;
• Genetic factors, such as HLA-B27 in SpA;
• Hormonal and metabolic disturbances, including vitamin D deficiency and secondary hyperparathyroidism; and
• Medication effects, particularly from glucocorticoids.

Although the exact contribution varies by disease, the imbalance between increased bone resorption and decreased bone formation is the central mechanism.

Q. How does chronic inflammation disrupt bone homeostasis?

Chronic inflammation disrupts bone homeostasis by shifting the physiological balance toward increased bone resorption. It is characterized by elevated levels of proinflammatory cytokines, including TNF-α, IL-1 and IL-6. These mediators promote osteoclastogenesis and enhance bone resorptive activity. At the molecular level, this is further mediated by an upregulation of the RANK/RANKL/osteoprotegerin axis, resulting in increased differentiation and activation of osteoclasts. In parallel, inhibition of the Wnt/β-catenin signalling pathway, driven by antagonists such as Dkk-1 and sclerostin, leads to impaired osteoblast differentiation and diminished bone formation.

Additional disease-specific factors contribute to this imbalance. For instance, RA autoantibodies, such as anti-CCP, have been shown to directly stimulate osteoclast differentiation. In SpA, genetic predisposition, particularly the presence of HLA-B27, is associated with alterations in bone metabolism. Furthermore, systemic hormonal and metabolic disturbances, including vitamin D deficiency and secondary hyperparathyroidism, further exacerbate skeletal deterioration. Iatrogenic factors also play a significant role, with glucocorticoid therapy representing a major contributor to bone loss across multiple rheumatologic conditions.

Although the relative contribution of these mechanisms varies between diseases, the fundamental pathophysiological hallmark remains a disruption of bone homeostasis, characterized by an imbalance between increased bone resorption and insufficient bone formation.

Q. What are the most important risk factors beyond inflammation?

Beyond the direct effects of inflammation, a number of additional risk factors substantially contribute to the development and progression of osteoporosis in patients with chronic inflammatory diseases. Among the most prominent is glucocorticoid therapy, which represents a major and well-established iatrogenic driver of bone loss due to its inhibitory effects on osteoblast function, promotion of osteocyte apoptosis and enhancement of osteoclast-mediated bone resorption. Furthermore, reduced mobility and physical inactivity, often resulting from pain, joint damage and functional impairment, lead to diminished mechanical loading of the skeleton, thereby accelerating bone loss.

Metabolic factors also play a critical role. Vitamin D deficiency, frequently observed in these patient populations as a consequence of malabsorption, limited sun exposure or disease-related factors, contributes to impaired calcium homeostasis and skeletal demineralization. This is often accompanied by secondary hyperparathyroidism, which further exacerbates bone resorption through increased parathyroid hormone activity. Hormonal alterations, including decreased levels of dehydroepiandrosterone (DHEA) and oestrogens, additionally impair bone metabolism by reducing the protective effects of sex steroids on bone turnover. Low body weight and malnutrition, particularly evident in conditions such as systemic sclerosis, further compromise bone integrity.

Importantly, these risk factors rarely occur in isolation; rather, they tend to coexist and interact, resulting in a cumulative and often synergistic increase in the risk of osteoporosis and fragility fractures.

Q. What are best practices for screening and managing osteoporosis in these patients?

Optimal management of osteoporosis in patients with chronic inflammatory diseases necessitates an early, proactive and multidisciplinary approach, integrating timely risk assessment with targeted therapeutic interventions.

Screening strategies should focus on the early identification of individuals at increased risk across the full spectrum of rheumatologic conditions. This includes the systematic assessment of bone mineral density, most commonly by dual-energy X-ray absorptiometry (DXA) or radiofrequency echographic multispectrometry (REMS). REMS offers the advantage of enabling BMD monitoring at shorter intervals and provides the opportunity to estimate fracture risk from as early as 20 years of age, compared with FRAX using DXA, which is typically applied after 40 years.

These assessments should be integrated with a comprehensive evaluation of disease-specific fracture risk. Importantly, existing general population models for fracture risk assessment fail to capture the full spectrum of relevant risk factors, highlighting the need for disease-adapted and individualized approaches.

Management should be multifaceted and directed both at the underlying disease process and at modifiable contributors to bone loss. Effective suppression of inflammatory activity through disease-modifying antirheumatic drugs (DMARDs) and biologic agents has been shown to exert a beneficial effect on bone metabolism. Concurrently, efforts should be made to minimize glucocorticoid use to the lowest effective dose and shortest possible duration.

Correction of metabolic abnormalities represents an additional cornerstone of therapy, including the optimization of vitamin D status and adequate calcium intake to support bone mineralization. Functional interventions, such as structured physical activity programs and rehabilitation strategies, are essential to counteract immobilization and maintain musculoskeletal integrity.

Given the complexity and heterogeneity of these patients, interdisciplinary collaboration is indispensable. Close coordination between rheumatology, endocrinology, radiology, orthopaedics and other relevant specialties enables the development of individualized prevention and treatment strategies tailored to each patient’s risk profile. Ultimately, the multifactorial nature of osteoporosis in inflammatory diseases requires a coordinated, long-term management strategy aimed at reducing fracture risk, preserving skeletal health and maintaining overall functional capacity and quality of life.