Bone mineral density and bone turnover in patients with psoriatic arthritis

Does the lifestyle of patients with psoriasis affect their illness?

Psoriasis is one of the most common chronic, incurable inflammatory skin diseases, affecting 2–4% of the general population. Etiopathogenesis of this disease remains unclear. It is widely considered to be a multifactorial disorder caused by the interaction between inherited susceptibility alleles and environmental risk factors, such as lifestyle, diet, stimulants, foci of inflammation, and psychological factors. The widespread prevalence of psoriasis is a very significant health and socioeconomic problem. Treatment of psoriasis is based on relieving the acute symptoms of the disease. Despite the implementation of many therapeutic options, including biological treatment, effectiveness of these options is not always sufficient, or in some patients it is not satisfactory. In order to properly control the symptoms of the disease, the patient should be told that the therapeutic effect is achieved not only by pharmacotherapy but also by introducing appropriate healthy habits in everyday life. This article discusses the importance of patient-controlled factors that affect the severity of psoriasis. Theimportance of regular exercise, smoking avoidance, and reduced alcohol consumption is explained, as well as the importance for psoriasis treatment of psychotherapy and spa therapy. Understanding the essence of these factors in the treatment of psoriasis is important in achieving satisfactory therapeutic effects.

Risk factors associated with osteoporosis and fracture in psoriatic arthritis

BACKGROUND

Although there are few studies mentioned there may be some relationship between psoriatic arthritis (PsA) and osteoporosis, clinical data in real world still need to be clarified in China. The aim of this study was to assess the areal and volumetric bone mineral density (BMD), frequency of fracture, and risk factors in patients with PsA.

METHODS

A total of one hundred PsA patients who visited Peking University First Hospital and one hundred age- and sex-matched healthy controls with DXA data were enrolled in the study. Patients with clinical fractures confirmed by X-ray during follow-up were also recorded. Clinical characteristics of the patients were recorded and compared between the abnormal BMD group and the normal BMD group, as well as between the fracture and non-fracture groups. Risk factors for fracture and low BMD were analyzed.

RESULTS

Mean BMD at the total hip and femoral neck was significantly lower in PsA patients than that in healthy controls (0.809 ± 0.193 vs. 0.901 ± 0.152 g/cm2, P  = 0.041; 0.780 ± 0.146 vs. 0.865 ± 0.166 g/cm2, P  = 0.037, respectively). Moreover, lumbar spine BMD was negatively correlated with psoriasis duration, swollen joint count and DAS28-CRP (r = -0.503, -0.580, -0.438; P < 0.05). Total hip BMD and femoral neck BMD were negatively correlated with HAQ (r = -0.521, -0.335; P < 0.05). Fractures occurred in 29 patients during the follow-up period. Logistic regression analysis showed that older age (OR 1.132 [95%CI: 1.026-1.248), P < 0.05], higher HAQ score (OR 1.493, 95%CI: 1.214-1.836, P < 0.01), higher disease activity index for psoriatic arthritis (OR 1.033, 95% CI: 1.002-1.679, P < 0.05) and hip joint involvement (OR 6.401, 95% CI: 4.012-44.180, P < 0.05) were risk factors for fracture in the multivariate model.

CONCLUSIONS

Increased risks of osteoporosis and fracture were found in PsA patients compared to healthy controls. Besides age, high disease activity and hip joint involvement were risk factors for decreased BMD and fracture.

Clinical, laboratory, and genetic markers for the development or presence of psoriatic arthritis in psoriasis patients: a systematic review

Twenty to thirty percent of psoriasis (Pso) patients will develop psoriatic arthritis (PsA). Detection of Pso patients that are (at risk for) developing PsA is essential to prevent structural damage. We conducted a systematic search of five bibliographic databases, up to May 2020. We searched for studies assessing markers (clinical, laboratory, genetic) associated with the development or presence of PsA in Pso patients. Study selection and quality assessment of the included studies was performed, followed by a qualitative best evidence synthesis to determine the level of evidence for a marker and its association with concomitant/developing PsA in Pso. Overall, 259 possible markers were identified in 119 studies that met the inclusion criteria. Laboratory markers related to inflammation and bone metabolism reached a strong level of evidence for the association (not prediction) of PsA in Pso. Only CXCL10 showed strong evidence for a positive predictive value for PsA in Pso. The importance of timely detecting PsA in a Pso population, and finding more (bio)markers contributing to early detection, remains high.

Characterization of bone metabolism in hungarian psoriatic arthritis patients: a case-control study

Background

Skeletal manifestations are predominant in psoriatic arthritis (PsA). The aim of this cross-sectional, case-control study is the complex assessment of areal and volumetric bone mineral density (BMD), fracture risk, vitamin D status and bone turnover markers, and its association with disease-related variables.

Methods

Lumbar spine (L1-L4) and femoral neck (FN) areal, and distal radius (DR) volumetric BMD, 10-year probability of major and hip osteoporotic fracture as assessed by the fracture risk assessment (FRAX) tool, markers of bone metabolism and disease activity were assessed.

Results

Upon comparison of the disease and age- and sex-matched control groups, there was a statistically significant difference in FN areal (0.952 (0.607–1.292) g/cm² vs. 1.016 (0.760–1.550) g/cm²; p = 0.001) and DR total volumetric (284.3 (138.9–470.3) mg/cm³ vs. 367.0 (287.0–412.0) mg/cm³; p < 0.001) BMD, 10 year probability for major osteoporotic (3.7% (0.7–32%) vs. 2.6% (0–17.5%); p = 0.003) and hip (0.4% (0–16%) vs. 0.05% (0–6.1%); p = 0.002) fracture and 25-hydroxyvitamin D status (47.5 (10–120) nmol/L vs. 64 (10–137; p < 0.001) nmol/L). As compared to areal assessment, volumetric BMD measurements identified a significantly higher number of patients with low bone mineral density (T-Score ≤ − 1.00) (34% vs. 88%, p < 0.001). Upon multiple linear regression analysis, disease activity score, as determined by DAS28 assessment, was an independent predictor of 10-year probability for major osteoporotic fracture (B (95%CI) = 1.351 (0.379–2.323); p = 0.007).

Conclusion

In the studied PsA cohort, disease activity was an independent predictor of 10-year probability for a major osteoporotic fracture, and complemented assessment of volumetric and areal BMD assured better efficacy at identifying those with low bone mineral density.

Prevalence and factors associated with osteoporosis and bone mineral density testing in psoriatic arthritis

OBJECTIVES

To determine bone mineral density (BMD) in psoriatic arthritis (PsA) patients, factors associated with undergoing BMD testing, and the effect of PsA clinical activity on BMD.

METHODS

Patients attending the University of Toronto PsA Clinic with a BMD from cohort inception to January 2019 were included. Descriptive statistics summarized lumbar spine, femoral neck and total hip T-scores. Cox proportional hazard regression identified predictors for BMD testing. Logistic regression analysis determined odds of having normal (T-score ≥ -1.0) versus osteoporotic range BMD (T-score ≤ -2.5). A multi-state model determined factors associated with BMD state changes over time.

RESULTS

Of the 1479 patients, 214 had BMDs. Mean T-scores at the lumbar spine, femoral neck and total hip were -0.30±0.32, -1.10±1.04 and -0.45±0.42 respectively. Osteopenia and osteoporosis occurred in 45.27% and 12.94% of patients. Increasing age, menopause, elevated acute phase reactants, biologic, methotrexate and systemic glucocorticoid use were associated with a higher chance of undergoing BMD testing. Increased BMI and biologic use were associated with a lower chance of having osteoporotic range BMD. In multi-state analysis, polyarthritis may portend lower BMDs over time, although this did not achieve statistical significance due to low patient numbers.

CONCLUSIONS

The prevalence of osteopenia and osteoporosis in the PsA cohort were similar to the general population. Clinicians are using osteoporosis risk factors and PsA disease severity markers to select patients for BMD testing. Polyarticular disease may portend worse BMDs. Biologic use and increased BMI appear to have a protective effect.

Bone phenotypes in rheumatology - there is more to bone than just bone

Osteoarthritis, rheumatoid arthritis, psoriatic arthritis, and ankylosing spondylitis, all have one clear common denominator; an altered turnover of bone. However, this may be more complex than a simple change in bone matrix and mineral turnover. While these diseases share a common tissue axis, their manifestations in the area of pathology are highly diverse, ranging from sclerosis to erosion of bone in different regions. The management of these diseases will benefit from a deeper understanding of the local versus systemic effects, the relation to the equilibrium of the bone balance (i.e., bone formation versus bone resorption), and the physiological and pathophysiological phenotypes of the cells involved (e.g., osteoblasts, osteoclasts, osteocytes and chondrocytes). For example, the process of endochondral bone formation in chondrocytes occurs exists during skeletal development and healthy conditions, but also in pathological conditions. This review focuses on the complex molecular and cellular taxonomy of bone in the context of rheumatological diseases that alter bone matrix composition and maintenance, giving rise to different bone turnover phenotypes, and how biomarkers (biochemical markers) can be applied to potentially describe specific bone phenotypic tissue profiles.

Systemic evaluation of the relationship between psoriasis, psoriatic arthritis and osteoporosis: observational and Mendelian randomisation study

OBJECTIVES AND METHODS

With 432 513 samples from UK Biobank dataset, multivariable linear/logistic regression were used to estimate the relationship between psoriasis/psoriatic arthritis (PsA) and estimated bone mineral density (eBMD)/osteoporosis, controlling for potential confounders. Here, confounders were set in three ways: model0 (including age, height, weight, smoking and drinking), model1 (model0 +regular physical activity) and model2 (model1 +medication treatments). The eBMD was derived from heel ultrasound measurement. And 4904 patients with psoriasis and 847 patients with PsA were included in final analysis. Mendelian randomisation (MR) approach was used to evaluate the causal effect between them.

RESULTS

Lower eBMD were observed in patients with PsA than in controls in both model0 (β-coefficient=-0.014, p=0.0006) and model1 (β-coefficient=-0.013, p=0.002); however, the association disappeared when conditioning on treatment with methotrexate or ciclosporin (model2) (β-coefficient=-0.005, p=0.28), mediation analysis showed that 63% of the intermediary effect on eBMD was mediated by medication treatment (p<2E-16). Patients with psoriasis without arthritis showed no difference of eBMD compared with controls. Similarly, the significance of higher risk of osteopenia in patients with PsA (OR=1.27, p=0.002 in model0) could be eliminated by conditioning on medication treatment (p=0.244 in model2). Psoriasis without arthritis was not related to osteopenia and osteoporosis. The weighted Genetic Risk Score analysis found that genetically determined psoriasis/PsA were not associated with eBMD (p=0.24 and p=0.88). Finally, MR analysis showed that psoriasis/PsA had no causal effect on eBMD, osteoporosis and fracture.

CONCLUSIONS

The effect of PsA on osteoporosis was secondary (eg, medication) but not causal. Under this hypothesis, psoriasis without arthritis was not a risk factor for osteoporosis.

Quantitative Imaging in Inflammatory Arthritis: Between Tradition and Innovation

Radiologic imaging is crucial for diagnosing and monitoring rheumatic inflammatory diseases. Particularly the emerging approach of precision medicine has increased the interest in quantitative imaging. Extensive research has shown that ultrasound allows a quantification of direct signs such as bone erosions and synovial thickness. Dual-energy X-ray absorptiometry and high-resolution peripheral quantitative computed tomography (CT) contribute to the quantitative assessment of secondary signs such as osteoporosis or lean mass loss. Magnetic resonance imaging (MRI), using different techniques and sequences, permits in-depth evaluations. For instance, the perfusion of the inflamed synovium can be quantified by dynamic contrast-enhanced imaging or diffusion-weighted imaging, and cartilage injury can be assessed by mapping (T1ρ, T2). Furthermore, the increased metabolic activity characterizing the inflammatory response can be reliably assessed by hybrid imaging (positron emission tomography [PET]/CT, PET/MRI). Finally, advances in intelligent systems are pushing forward quantitative imaging. Complex mathematical algorithms of lesions' segmentation and advanced pattern recognition are showing promising results.

Fragility fractures in psoriatic arthritis patients: a matched retrospective cohort study

OBJECTIVE

To compare incidental fragility fractures in psoriatic arthritis (PsA) patients with matched controls from a university hospital.

METHODS

Consecutive PsA patients were matched (age and sex) with controls (1:2). Follow-up began at index date, defined as the date of PsA diagnosis for cases and their respective controls, until the last hospital visit, death or the end of the study (31 December 2017). Electronic medical records were reviewed for osteoporotic fractures. Incidence rates per 100,000 persons-years (PY) of distinct types of fractures after index dates were calculated and compared between groups. A multivariate Cox regression analysis was performed to investigate determinants of fractures.

RESULTS

Ninety-two PsA patients and 184 controls were included. No difference was found in the overall fracture incidence rate per 100,000 PY between PsA and controls (1020 95% CI 510-1930, vs 870 95% CI 520-1390, p = 0.36). Vertebral fractures were numerically more frequent in PsA patients with an incidence rate of 1020 (95% CI 510-1930) per 100,000 PY versus 460 (95% CI 240-920), per 100,000 PY in the control group but it did not reach statistical significance (p = 0.06). In the Cox regression analysis, after adjusting for bisphosphonate use, only age (HR 1.10, 1.05-1.16, p < 0.001) and female sex (HR 3.94, 1.11-13.91, p = 0.03) were associated with fractures while PsA diagnosis and use of glucocorticoids were not.

CONCLUSION

In this cohort of PsA patients, no overall increased risk of fractures was found in comparison with matched controls. Key Points • PsA could have different effects on bone, leading to confusing results in bone densitometry readings contributing to the difficulty in establishing the real prevalence of OP in PsA. • Vertebral fractures were more frequent in PsA patients compared to controls, but it did not reach statistical significance. No difference was found in the overall fracture incidence rate.

Osteoporosis and Psoriasis

Psoriasis is a chronic inflammatory disease associated with multiple comorbidities, particularly in patients with arthritis or more severe forms of the disease. The link between all these comorbidities is probably systemic inflammation. Several recent studies have indicated that patients with psoriasis may be at an increased risk of pathologic fractures and osteoporosis. Current guidelines on comorbidities in psoriasis do not recommend assessment of bone health. In this article, we review the available evidence on the association between psoriasis and osteoporosis. We first examine the concept of osteoporosis and the role of vitaminD in bone health and then propose an algorithm for managing and treating this condition in patients with psoriasis.

Changes in body composition and bone mineral density in postmenopausal women with psoriatic arthritis

Objective

Prolonged inflammation status due to psoriatic arthritis (PsA) may contribute to the loss of muscle mass, extending from muscle weakness, and increased risk of falls and fractures. The risk of fractures and their complications increases with concomitant osteoporosis.

Material and methods

The study included 95 women aged 50–75 years. The presence of sarcopenia was evaluated in a group of 51 women with PsA, and 44 controls (without inflammatory joint disease). Measurements of muscle mass and lean body mass were made using the method of bioimpedance assessing ALM (Appendicular Lean Mass) index and SMI (Skeletal Muscle Index). The diagnosis of sarcopenia was made in women with low muscle mass and concomitant reduction of the efficiency of the assessed functional test Timed Up and Go (TUG). Bone density measurement was done by densitometry in the femoral neck and lumbar spine. (Ethics statement OIL 625/16/Bioet).

Results

Sarcopenia, using ALM index and SMI, was diagnosed in 13.7% and 43.1% of PsA women, and in healthy women in 9% and 20.4%, respectively. In the group of PsA, sarcopenia was associated with a significant increase in the occurrence of disorders of bone mineralisation (72.7% vs. 41.3% in patients without a decrease in muscle mass). There was no correlation between the loss of muscle mass, bone density, and activity of PsA.

Conclusions

The prevalence of sarcopenia in postmenopausal women suffering from PsA is associated with the occurrence of osteoporosis.

KIF3A and IL-4 are disease-specific biomarkers for psoriatic arthritis susceptibility

To date, the genes associated with Psoriatic Arthritis (PsA) are principally involved in inflammation, immune response and epidermal differentiation, without any information about the relationship between disease and bone metabolism genes. Our work was focused on 5q31 locus, which contains several genetic variants significantly associated with PsA. The study involved 1526 subjects (500 PsA, 426 PsV, 600 controls). The region was evaluated by selecting and genotyping the SNPs of interest by Real Time PCR and direct sequencing. The results were subjected to biostatistic and bioinformatic analysis.

The case-control study highlighted a significant association between KIF3A/IL-4 and PsA, but not with PsV (Psoriasis Vulgaris) patients. In addition, the haplotype analysis revealed two haplotypes significantly associated with PsA susceptibility. The Linkage Disequilibrium (LD) study showed the presence of a specific block in high LD within 132,692,628-132,737,638 bp of 5q31, giving additional evidence of specific association of the 5q31 region in PsA patients. Moreover, KIF3A expression was assessed by immunohistochemistry assays which showed a marked and significant difference of KIF3A expression between pathological and normal tissues. Our analysis described KIF3A and IL-4 as novel susceptibility genes for PsA, suggesting a clear implication of bone metabolism genes in the disease etiopathogenesis.

Cardiovascular risk assessment in osteoporotic patients using osteoprotegerin as a reliable predictive biochemical marker

Osteoprotegerin (OPG), a member of the tumour necrosis factor receptor (TNFR) superfamily of proteins known to be involved in a large number of biological systems, plays a pivotal role in bone remodelling. In addition to the roles of OPG in bone metabolism, it has been reported to be associated with a high cardiovascular risk in patients with metabolic syndrome. In most cases, the exact functions of OPG remain to be established; however, the widespread expression of OPG suggests that this molecule may have multiple biological activities, mainly in the cardiometabolic environment. The aim of this study was to evaluate the value of OPG as a predictive marker for cardiovascular and metabolic risk in osteoporotic patients. The study group comprised patients with osteoporosis, in order to evaluate the association between OPG serum levels and cardiovascular pathology. Our results revealed significant correlations between classical biochemical bone and metabolic parameters, such as osteocalcin and parathyroid hormone with lipid and glucose biomarkers, sustaining the crosstalk between calcium and bone parameters and cardiovascular risk. The OPG serum level proved to have a significant and independent predictive value for metabolic syndrome (MetS) as a cardiovascular risk standard in osteoporotic patients. The OPG serum levels were increased in patients with MetS as a protective response against the atherosclerotic lesions. The serum levels of 25-hydroxy vitamin D had significant and independent predictive value for cardiovascular and metabolic risk in our subjects, sustaining the active role of vitamin D beyond the area of bone metabolism.

Psoriasis, fracture risk and bone mineral density: the HUNT Study, Norway

BACKGROUND

An association between psoriasis and osteoporosis has been reported.

OBJECTIVES

To investigate, in a large prospective population-based Norwegian study, whether psoriasis is associated with increased risk of forearm or hip fracture; to investigate the cross-sectional association between psoriasis and bone mineral density (BMD) T-score in a subpopulation.

METHODS

Hospital-derived fracture data from Nord-Trøndelag County (1995-2013) were linked to psoriasis information, BMD measurements and lifestyle factors from the third survey of the Nord-Trøndelag Health Study 2006-08 (HUNT3); socioeconomic data from the National Education Database; and use of medication from the Norwegian Prescription Database.

RESULTS

Among 48 194 participants in HUNT3, we found no increased risk of forearm or hip fracture in 2804 patients with self-reported psoriasis [overall age- and sex-adjusted hazard ratio 1·03, 95% confidence interval (CI) 0·82-1·31]. No clear association was found between psoriasis and mean BMD T-score; overall age- and sex-adjusted differences in total hip, femoral neck and lumbar spine BMD T-scores were 0·02 (95% CI -0·11 to 0·14), 0·05 (95% CI -0·06 to 0·17) and 0·07 (95% CI -0·09 to 0·24), respectively. No clear association was found between psoriasis and prevalent osteoporosis in either total hip, femoral neck or lumbar spine; overall age- and sex-adjusted odds ratio was 0·77 (95% CI 0·54-1·10). Associations did not change substantially after adjustment for education, smoking, systemic steroid use and body mass index.

CONCLUSIONS

We found no association between psoriasis and risk of fracture. The study did not indicate reduced BMD T-score or higher prevalence of osteoporosis among patients with psoriasis.

Structure and Property Changes in Self-Assembled Lubricin Layers Induced by Calcium Ion Interactions

Lubricin (LUB) is a "mucin-like" glycoprotein found in synovial fluids and coating the cartilage surfaces of articular joints, which is now generally accepted as one of the body's primary boundary lubricants and antiadhesive agents. LUB's superior lubrication and antiadhesion are believed to derive from its unique interfacial properties by which LUB molecules adhere to surfaces (and biomolecules, such as hyaluronic acid and collagen) through discrete interactions localized to its two terminal end domains. These regionally specific interactions lead to self-assembly behavior and the formation of a well-ordered "telechelic" polymer brush structure on most substrates. Despite its importance to biological lubrication, detailed knowledge on the LUB's self-assembled brush structure is insufficient and derived mostly from indirect and circumstantial evidence. Neutron reflectometry (NR) was used to directly probe the self-assembled LUB layers, confirming the polymer brush architecture and resolving the degree of hydration and level of surface coverage. While attempting to improve the LUB contrast in the NR measurements, the LUB layers were exposed to a 20 mM solution of CaCl₂, which resulted in a significant change in the polymer brush structural parameters consisting of a partial denaturation of the surface-binding end-domain regions, partial dehydration of the internal mucin-domain "loop", and collapse of the outer mucin-domain surface region. A series of atomic force microscopy measurements investigating the LUB layer surface morphology, mechanical properties, and adhesion forces in phosphate-buffered saline and CaCl₂ solutions reveal that the structural changes induced by calcium ion interactions also significantly alter key properties, which may have implications to LUB's efficacy as a boundary lubricant and wear protector in the presence of elevated calcium ion concentrations.

Psoriasis: new comorbidities

Psoriasis is a chronic inflammatory disease associated with several comorbidities. A few decades ago, it was considered an exclusive skin disease but today it is considered a multisystem disease. It is believed that 73% of psoriasis patients have at least one comorbidity. Studies have demonstrated the association of psoriasis with inflammatory bowel disease, uveitis, psychiatric disorders, metabolic syndrome and its components and cardiovascular diseases. The systemic inflammatory state seems to be the common denominator for all these comorbidities. This work aims at presenting a review of the current literature on some new comorbidities that are associated with psoriasis as osteoporosis, obstructive sleep apnea and chronic obstructive pulmonary disease. While there is still controversy, many studies already point to a possible bone involvement in patients with psoriasis, especially in the male group, generally less affected by osteoporosis. Psoriasis and chronic obstructive pulmonary disease present some risk factors in common as obesity, smoking and physical inactivity. Besides, both diseases are associated with the metabolic syndrome. These factors could be potential confounders in the association of the two diseases. Further prospective studies with control of those potential confounders should be developed in an attempt to establish causality. Existing data in the literature suggest that there is an association between obstructive sleep apnea and psoriasis, but studies performed until now have involved few patients and had a short follow-up period. It is, therefore, premature to assert that there is indeed a correlation between these two diseases.

Quantitative and Qualitative Changes of Bone in Psoriasis and Psoriatic Arthritis Patients

Psoriatic arthritis (PsA) is a chronic inflammatory disease characterized by periarticular bone loss and new bone formation. Current data regarding systemic bone loss and bone mineral density (BMD) in PsA are conflicting. The aim of this study was to evaluate bone microstructure and volumetric BMD (vBMD) in patients with PsA and psoriasis. We performed HR-pQCT scans at the ultradistal and periarticular radius in 50 PsA patients, 30 psoriasis patients, and 70 healthy, age- and sex-related controls assessing trabecular bone volume (BV/TV), trabecular number (Tb.N), inhomogeneity of the trabecular network, cortical thickness (Ct.Th), and cortical porosity (Ct.Po), as well as vBMD. Trabecular BMD (Tb.BMD, p = 0.021, 12.0%), BV/TV (p = 0.020, -11.9%), and Tb.N (p = 0.035, 7.1%) were significantly decreased at the ultradistal radius and the periarticular radius in PsA patients compared to controls. In contrast, bone architecture of the ultradistal radius and periarticular radius was similar in patients with psoriasis and healthy controls. Duration of skin disease was associated with low BV/TV and Tb.N in patients with PsA. These data suggest that trabecular BMD and bone microstructure are decreased in PsA patients. The observation that duration of skin disease determines bone loss in PsA supports the concept of subclinical musculoskeletal disease in psoriasis patients.

Factors associated with bone mineral density loss in patients with spondyloarthropathies: A 4-year follow-up study

OBJECTIVE

To explore the relationship between laboratory, functional, disease activity markers and bone mineral density (BMD) loss in patients with spondyloarthropathies (SpAs).

METHODS

A cohort of 41 SpA patients were followed up for 4 years. Disease activity indices, spinal mobility and laboratory tests, BMD using were monitored at the baseline and 4-year follow-up. The 4% BMD loss at either of the proximal femurs was defined as significant.

RESULTS

Over the 4-year study period, 27% of SpA patients experienced femoral BMD loss. Baseline BMD>0.85g/cm(2) (p=0.011) was the baseline factor associated with BMD loss at 4-year follow-up. Several clinical and functional tests were helpful in identifying the BMD loss at follow-up: CRP>15.6mg/L (sens. 91%, spec. 70%), ESR>29mm/h (sens. 82%, spec. 73%), Bath Ankylosing Spondylitis Disease Activity Index (BASDAI)>4.75 (sens. 91%, spec. 62%). At follow-up anti-TNFα treatment history, stable or improved lateral flexion and intermalleolar distance (NPV, accordingly, 95%, 88% and 87%), made BMD loss unlikely. Deterioration of the physician assessment of global disease activity (PAGDA) score from baseline to follow-up was a remarkable predictor of BMD loss (PPV=0.83), while stable or improved score excluded the BMD loss (NPV=0.83). According to multiple logistic regression analysis, baseline BMD value and follow-up CRP levels, when considered together, identify BMD status correctly in 85% of SpA patients (Nagelkerke R(2)=0.676).

CONCLUSION

Baseline BMD, anti-TNFα treatment, PAGDA score, spinal mobility tests and disease activity markers are useful factors in predicting the BMD loss in SpA patients and can provide surrogate information on BMD status.

Vitamin D status in men with psoriatic arthritis: a case-control study

We determined hypovitaminosis D prevalence in men with psoriatic arthritis. This is a cross-sectional, analyst blinded, age- and sex-matched, case-control study. Men with psoriatic arthritis have significantly lower 25-hydroxyvitamin D levels. Men with psoriatic arthritis are at increased odds of suffering from hypovitaminosis D.

INTRODUCTION

Skeletal manifestations as a result of abrupted bone metabolism may be predominant in psoriatic arthritis (PsA). Vitamin D plays a vital role in maintenance of skeletal health and is known to modulate the immune system in various autoimmune diseases including PsA. The aim of the present study was to determine the prevalence of hypovitaminosis D in a treatment naïve, de novo psoriatic arthritis male cohort in a cross-sectional, analyst blinded, age- and sex-matched, case-control study.

METHODS

25 hydroxyvitamin D (25OHD), parathyroid (PTH), osteocalcin (OC) and C-terminal telopeptides of type-I collagen (CTx) levels, and lumbar spine and femoral neck bone mineral density were compared between 53 PsA and controls.

RESULTS

The prevalence of hypovitaminosis D (25 hydroxyvitamin D (25OHD) levels <75 nmol/L) was 81 and 57 % in the PsA and control groups, respectively. Compared to the healthy controls, 25OHD (67.2 (12-137) nmol/L vs. 51.9 (15-95) nmol/L; p = 0.001) was significantly lower, and osteocalcin (13.6 (5-33) μg/L vs. 18.2 (6-35) μg/L; p = 0.003) and C-terminal telopeptides of type-I collagen (0.20 (0.01-0.71) μg/L vs. 0.28 (0.06-0.69) μg/L; p = 0.008) were significantly higher in the PsA group. A significant association was found between hypovitaminosis D and PsA; the odds for patients with PsA of having hypovitaminosis D was 3.297 (95 % confidence interval 1.372 to 7.922).

CONCLUSION

The results of this study suggest that men with PsA have significantly lower 25-hydroxyvitamin D levels, and furthermore, men with PsA are at statistically significant increased odds of suffering from hypovitaminosis D.

Vitamin D3 levels and bone mineral density in patients with psoriasis and/or psoriatic arthritis

Limited data are available on the vitamin D3 status and bone mineral density (BMD) of patients with psoriasis or with psoriatic arthritis. Our study intended to explore possible correlations between vitamin D status and BMD, as well as among these parameters and the features of the underlying disorder. Seventy-two patients with psoriasis/or psoriatic arthritis (female : male ratio, 40:32; mean age, 58.5 ± 11.6 years; mean duration of follow up, 142.7 ± 147.7 months) participated in the study. We evaluated the characteristic clinical features of the underlying disease, performed bone densitometry of the lumbar spine and the hip region, measured the serum vitamin 25(OH)D3 levels of the patients, and undertook the statistical analysis of the relationships between the clinical and the laboratory parameters. The proportion of patients with a low BMD value did not exceed that seen in the general population. We found an inverse correlation between the serum level of vitamin 25(OH)D3 and body mass index, as well as between the former and the severity of skin involvement. Furthermore, the activity of psoriatic arthritis was significantly higher in patients with inadequate vitamin D3 status. In patients with psoriatic arthritis, BMD significantly exceeded the values measured in patients suffering from psoriatic skin lesions only. Our findings suggest the importance of evaluating the vitamin D3 status and screening for comorbid conditions in patients with psoriasis or psoriatic arthritis. This appears justified, in particular, due to the possible role of hypovitaminosis D3 in provoking the development of skin lesions and joint symptoms.

Osteoporosis in rheumatic diseases

Rheumatic diseases, characterized by chronic inflammation and damage to various organs and systems, include systemic lupus erythematosus, rheumatoid arthritis, ankylosing spondylitis and other connective tissue diseases. Bone is a target in many inflammatory rheumatic diseases. In recent years, the survival of patients with rheumatic diseases has increased markedly and the relationship between rheumatic diseases and osteoporosis (OP) has become more prominent. OP and related fragility fractures increase the morbidity and mortality of rheumatic disease. The cause of OP in rheumatic diseases is complex. The pathogenesis of OP in rheumatic diseases is multifactorial, including disease and treatment-related factors. Osteoimmunology, a crosstalk between inflammatory and bone cells, provides some insight into the pathogenesis of bone loss in systematic inflammatory diseases. The aim of this article is to review different risk factors in rheumatic diseases. Several factors play a role, such as chronic inflammation, immunological factors, traditional factors, metabolism and drug factors. Chronic inflammation is the most important risk factor and drug treatment is complex in patients with OP and rheumatic disease. Attention should be paid to bone loss in rheumatic disease. Optimal treatment of the underlying rheumatic disease is the first step towards prevention of OP and fractures. Apart from that, a healthy lifestyle is important as well as calcium and vitamin D supplementation. Bisphosphonates or denosumab might be necessary for patients with a low T score.

Serum soluble bone turnover biomarkers in psoriatic arthritis and psoriatic spondyloarthropathy

Because psoriatic arthritis (PsA) is an inflammatory disease of joints, serum soluble biomarkers specific for chronic joint and bone inflammation may predict future disease severity and response to therapy, thereby informing stratified medicine approaches. The objectives of our systematic review were to determine whether serum soluble bone and cartilage turnover biomarkers are (1) associated with PsA or psoriatic spondyloarthropathy; and (2) associated with disease activity, disease severity, or clinical phenotype. Ten studies met eligibility criteria. Matrix metalloproteinase (MMP)-3, Dickkopf (DKK)-1, macrophage colony-stimulating factor (M-CSF), crosslinked telopeptide of collagen-1, and tumor necrosis factor-related apoptosis-inducing ligand were associated with PsA, with equivocal results for osteoprotegerin (OPG) and bone alkaline phosphatase (ALP). MMP-3, DKK-1, M-CSF, CPII:C2C (ratio of cartilage degradation vs byproduct formation), and possibly OPG were associated with PsA independently of psoriasis. C1-2C (a neoepitope released when type 2 cartilage is degraded by collagenases) was associated with both tender and swollen joint counts, and bone morphogenetic protein-4 with patient global assessment of disease, pain score, and the Bath Ankylosing Spondylitis Disease Activity Index. Bone ALP was associated with disease activity. M-CSF and receptor activator of nuclear factor-κB ligand were associated with several plain radiographic features. No studies have investigated biomarker associations specifically with axial PsA.

Psoriasis and bone mineral density: implications for long-term patients

Psoriasis is a chronic inflammatory disease associated with several comorbidities. Osteoporosis is defined as a reduction in bone mineral density with impaired bone microarchitecture. Several mechanisms may be implicated as a possible cause for the association between psoriasis and osteoporosis, such as systemic inflammation, anti-psoriatic drug intake and joint dysfunction for psoriatic arthritis (PsA). The aim of the present study was to assess bone mineral density (BMD) in patients with psoriasis, correlating the prevalence of osteopenia/osteoporosis with Psoriasis Area and Severity Index (PASI) score, mean duration of psoriatic disease, PsA and previous treatments for psoriasis. Forty-three consecutive patients with psoriasis, 19 of whom were affected by the arthropathic form, were enrolled. We evaluated the severity of psoriasis as measured by PASI score, the CASPAR criteria and ultrasounds of the joints to verify the diagnosis of PsA and the age of psoriasis onset to estimate mean disease duration. Patients underwent a bone density scan of the lumbar spine and femoral neck by dual-energy X-ray absorptiometry to measure BMD. Patients with osteopenia/osteoporosis showed a statistically significant longer average duration of psoriatic disease (17 years), compared to patients affected by psoriasis with normal T-score (8.8 years) (P = 0.04). The linear logistic regression confirms a significant relation between mean psoriatic disease duration and BMD alterations (P = 0.04). Our results suggest the necessity of an early diagnostic evaluation of bone metabolism in patients with psoriasis, especially if characterized by longer disease duration.

Association between osteoporosis and psoriasis: results from the Longitudinal Health Insurance Database in Taiwan

This population-based analysis explored the association between osteoporosis and a previous diagnosis of psoriasis. We found that the adjusted odds ratio (OR) of having been previously diagnosed with psoriasis for subjects with osteoporosis was 1.65 (95 % confidence interval [CI], 1.42-1.94) when compared to controls.

INTRODUCTION

Although previous studies have investigated this association between psoriasis and osteoporosis, significant controversy remains regarding its presence. Therefore, this study set out to explore the association between osteoporosis and a previous diagnosis of psoriasis through a population-based case-control study in Taiwan.

METHODS

We identified 17,507 cases with a diagnosis of osteoporosis and randomly extracted 52,521 controls without a history of osteoporosis. We used conditional logistic regression analyses to calculate the OR for having been previously diagnosed with psoriasis.

RESULTS

Subjects with osteoporosis had a significantly higher prevalence of previously diagnosed psoriasis (1.50 % vs. 0.87 %, p < 0.001) compared to controls. Conditional logistic regression analysis revealed that the OR of having been previously diagnosed with psoriasis for subjects with osteoporosis was 1.65 (95 % CI, 1.42-1.94) when compared to controls after adjusting for monthly income, hypertension, diabetes, coronary heart disease, hyperlipidemia, rheumatoid arthritis, stroke, renal disease, Parkinson's disease, hyperthyroidism, chronic hepatopathy, Cushing's syndrome, malabsorption, tobacco use disorder, obesity, alcohol abuse/alcohol dependence syndrome, the use of SSRIs, and the use of systemic glucocorticoids. Furthermore, osteoporosis was significantly associated with a previous diagnosis of psoriasis in both sexes; the adjusted OR of prior psoriasis for cases when compared to controls was 1.52 (95 % CI, 1.16-1.99) and 1.73 (95 % CI, 1.44-2.13) for males and females, respectively. We also found that the adjusted OR of prior severe psoriasis for cases was 1.96 (95 % CI, 1.37-2.81) that of controls.

CONCLUSIONS

This investigation succeeded in detecting an association between osteoporosis and prior psoriasis among both men and women.

Periarticular bone gain at proximal interphalangeal joints and changes in bone turnover markers in response to tumor necrosis factor inhibitors in rheumatoid and psoriatic arthritis

OBJECTIVE

Rheumatoid arthritis (RA) and psoriatic arthritis (PsA) are characterized by periarticular bone erosion; periarticular bone formation is a feature in PsA. The effect of anti-tumor necrosis factor-α (TNF-α) on periarticular bone remodeling is unclear in both diseases. Our aim was to assess the response of bone turnover markers (BTM) and hand bone mineral density (BMD) to anti-TNF over 3 years in RA and PsA.

METHODS

We measured serum bone-specific alkaline phosphatase (bone ALP), procollagen type-I N-propeptide (PINP), intact osteocalcin, C-terminal cross-linking telopeptides (CTX-I), urinary N-terminal cross-linking telopeptide of type-I collagen (NTX-I), and free deoxypyridinoline crosslinks (fDPD) at baseline, 1, 12, and 36 months. BMD measurements (hands/spine/hip) were obtained at 3 timepoints.

RESULTS

We recruited 62 patients (RA 35; PsA 27). BTM correlated significantly with hand BMD but not with central BMD. Low hand BMD was associated with RA and increased BTM. Following anti-TNF therapy, hip BMD declined while spine and hand BMD were unchanged. Periarticular BMD at proximal interphalangeal (PIP) joints increased while it decreased at metacarpophalangeal joints. Bone ALP increased steadily and was always higher in PsA. PINP and intact osteocalcin increased to a lesser extent, but resorption markers did not change.

CONCLUSION

At baseline, hand BMD was inversely associated with BTM. Bone formation rather than resorption markers better showed the bone response to anti-TNF. Despite a lack of effect on central BMD, the modest effect of anti-TNF on PIP BMD may provide evidence that BTM reflect specifically bone remodeling activity at periarticular sites of inflammation in RA and PsA.

High frequency of vertebral fractures in early spondylarthropathies

We demonstrated that vertebral fractures (VF) are commonly found in early SpA. Patients with VF had lower lumbar BMD than patients without VF. VF remained frequently 'unrecognized' and untreated. VF have been associated with more back pain, reduced Qol, and increased risk of future fractures which stresses the importance of recognition also in early stage SpA.

INTRODUCTION

VF are a common complication of long-standing ankylosing spondylitis (AS). However, data of VF in early AS patients and in other spondylarthropathies (SpA) are scarce. Therefore we examined the prevalence of VF in early SpA patients and investigated the associations between VF and demographic and disease-related variables.

METHODS

SpA patients were included consecutively and radiographs of the spine were made. VF were assessed according to the method of Genant et al.: fractures were defined as reduction of ≥20% of the vertebrae. Descriptive statistics, t-tests and logistic regression analyses were used to study the relationship between VF and demographic and disease-related variables, radiographic damage and BMD.

RESULTS

A total of 113 early SpA patients were included with a disease duration of 7 months, a mean age of 37 years. Seventeen patients (15%) had at least one VF. Fourteen patients had one VF, three patients had two VF. Most VF were located at Th6-Th8. In patients with VF, bone mineral density (BMD) of lumbar spine was lower than BMD of patients without VF (t-test: p = 0.043). Axial Psoriatic Arthritis (PsA) was significantly associated with a higher risk for VF (odds ratio [OR]: 4.62, 95% confidence interval [CI] 1.15-18.58, p = 0.031). No significant associations were found with disease activity variables nor with radiographic severity.

CONCLUSION

In a group of 113 early, young SpA patients, 15% already had at least one VF. Most VF were asymptomatic, undetected by routine diagnostic procedures and located at the mid-thoracic spine. The VF were associated with low BMD of the lumbar spine and with axial PsA.

Osteoporosis in psoriatic arthritis: is there any?

AIMS

Although considered as a feature of inflammatory rheumatic diseases, there is a lot of controversy around low bone mass in patients with psoriatic arthritis. The aim of this cross-sectional study was to analyze bone mineral density in patients with psoriatic arthritis, as well as to investigate its possible association with some measures of disease activity and functional capacity.

SUBJECTS AND METHODS

Sixty-nine patients with established psoriatic arthritis (mean age 56.20 ± 12.23 years) and who have not been treated with specific antiosteoporotic drugs were recruited from the out-patient clinic database. Bone mineral density was measured by dual-energy X-ray absorptiometry at the lumbar spine and at the left hip. Disease activity measures included: duration of morning stiffness, tender and swollen joint count, patient's and physician's global assessment, presence of dactylitis and enthesitis, ESR, CRP and Disease Activity Score 28. Health Assessment Questionnaire was used to assess functional status.

RESULTS

According to WHO definition, spinal osteoporosis was found in 7.2% of patients, total hip osteoporosis in 1.4% of patients and femoral neck osteoporosis in 2.9% of patients. There was no significant association of any of the measures of disease activity with BMD at any site. Higher HAQ scores were associated with lower total hip BMD.

CONCLUSIONS

In our sample of patients with psoriatic arthritis we did not find increased prevalence of osteoporosis. There was no association of BMD with indices of disease activity, while negative correlation was found between HAQ and total hip BMD.

Assessment of osteoporosis in psoriasis with and without arthritis: correlation with disease severity

BACKGROUND

The most frequent extracutaneous association with psoriasis is arthritis. Because proinflammatory cytokines are increased in psoriasis, patients with this disease may be more prone to osteoporosis than the healthy individuals.

METHODS

We evaluated 50 patients with psoriasis, with or without psoriatic arthritis (PsA), for the presence and degree of osteoporosis by performing dual energy x-ray absorptiometry (DEXA) and obtaining serum osteoprotegrin (OPG) levels. In addition, we correlated these results with the extent of skin and joint disease. Psoriasis area and severity index (PASI) was determined in all 50 patients with psoriasis, and total joint score (TJS) was recorded in the 16 patients who also had PsA. Results of DEXA and serum OPG were also obtained for 20 healthy individuals who served as controls.

RESULTS

Osteoprotegrin level was significantly increased in psoriasis patients (with or without PsA) vs. controls. However, DEXA revealed that PsA patients had a higher degree of osteoporosis in the femur neck and wrist. In PsA patients, TJS correlated positively with both disease duration and PASI but correlated negatively with Z score of the femur.

CONCLUSION

Psoriasis patients with or without arthritis may suffer from osteoporosis as evidenced by significantly increased serum OPG. Prolonged and extensive cutaneous disease is an important risk factor for the development and severity of PsA. Patients with a greater number of affected joints are at higher risk of osteoporosis.

Bone mineral density and body composition in postmenopausal women with psoriasis and psoriatic arthritis

Introduction

The aim of the present study was to compare bone mineral density (BMD) and body composition (BC) measurements as well as identify risk factors for low BMD and osteoporotic fractures in postmenopausal women with psoriasis (Ps) and psoriatic arthritis (PsA).

Methods

A cross-sectional study was carried out in 45 PsA women, 52 Ps women and 98 healthy female controls (HC). Clinical risk factors for low bone density and osteoporotic fracture were evaluated by a specific questionnaire. An X-ray absorptiometry (DXA) at the lumbar spine, total femur and total body was performed on all patients. Skin and joint outcomes were measured by specific tools (PASI, HAQ and DAS28). Morphometric vertebral fractures were evaluated by lumbar and thoracic spine X-ray, according to Genant's method.

Results

There were no significant differences in age, body mass index (BMI), total lean mass and bone mineral density among the groups. However, the PsA group had a significantly higher body fat percentage (BF%) than the Ps and HC groups. Osteoporotic fractures were more frequently observed in PsA and Ps groups than in the HC group (P = 0.01). Recurrent falls and a longer duration of disease increased the risk of fracture (odds ratio (OR) = 18.3 and 1.08, respectively) in the PsA group (P = 0.02). Disability was the main factor related to osteoporotic fracture in the Ps group (odds ratio (OR) = 11.1) (P = 0.02).

Conclusions

Ps and PsA patients did not present lower BMD. However, they had a higher prevalence of osteoporotic fractures and higher risk of metabolic syndrome. Patients with a longer duration of disease, disability and recurrent falls need preventive measures.

Managing comorbid disease in patients with psoriatic arthritis

Psoriatic arthritis (PsA) is a unique type of inflammatory arthritis that is associated with skin psoriasis. The concept that PsA is simply a skin and joint disease has been challenged by large epidemiologic studies that link PsA with substantial comorbidity. Important comorbidities related to PsA include premature cardiovascular disease, infectious complications, malignancy risk, osteoporosis, and reduced quality of life. This review focuses on the prevalent comorbid diseases in patients with PsA and highlights how the presence of these associated comorbidities can affect the management of these patients.

Comparative analysis of disease activity measures, use of biologic agents, body mass index, radiographic features, and bone density in psoriatic arthritis and rheumatoid arthritis patients followed in a large U.S. disease registry

OBJECTIVE

To compare disease activity, radiographic features, and bone density in psoriatic arthritis (PsA) and rheumatoid arthritis (RA) matched cohorts.

METHODS

Disease activity and radiographic data in the Consortium of Rheumatology Researchers of North America database from 2001 to 2008 were compared for 2481 patients with PsA and 17,107 patients with RA subsequently matched for age, gender, and disease duration. Radiographic outcomes included presence of erosions, and joint deformity. In addition, bone mineral density (BMD) scores for lumbar spine (L-spine) and femoral neck were compared using the same matching criteria plus weight and smoking status.

RESULTS

Tender (4.5 vs 3.4, p < 0.001) and swollen (4.4 vs 2.9, p < 0.012) joint counts, and modified Health Assessment Questionnaire scores were significantly higher (0.4 vs 0.3, p < 0.001) in patients with RA compared with patients with PsA. Patient general health and pain scores were also higher in patients with RA vs patients with PsA. Joint erosions (47.4% vs 37.6%, p = 0.020) and deformity (25.2% vs 21.6%, p = 0.021) were more prevalent in RA than PsA. In multivariate analysis, a reduced prevalence of erosions in PsA vs RA was noted (OR 0.609, p < 0.001). After matching, T-scores for L-spine (-0.54 vs -0.36, p = 0.077) and femoral neck (-0.88 vs -0.93, p = 0.643) were similar in patients with RA and patients with PsA, although body weight was a major confounder.

CONCLUSION

The level of disease activity and radiographic damage was significantly higher for RA vs PsA subjects, although the magnitude of differences was relatively small. BMD levels were comparable between cohorts. Outcomes in patients with PsA and patients with RA may be more similar than previously reported.

Symptomatic osteochondroma of the spine in elderly patients

Whereas osteochondroma is a common benign bone tumor in adolescence, it is rarely observed in elderly patients. It is unknown why osteochondromas, which usually develop during skeletal growth, rarely develop in elderly patients. The authors report 3 cases of symptomatic spinal osteochondroma in elderly patients and discuss the possible reasons for the onset of the enlargement of osteochondromas in elderly patients.

Clinical history, radiographs, MR images, and CT myelography studies were obtained in each patient and are described. A review of the relevant literature is also presented. In the first case, the cervical osteochondroma caused spinal canal compression and occipital nerve irritation. It was totally excised, which successfully relieved the pain and allowed the patient to return to normal neurological function. In the second case, total removal of the tumor was effective in alleviating clinical symptoms. In the last case, ablation of the articular facet joint partially relieved the patient's lower-back pain. In the first 2 cases, the patients suffered from psoriasis and associated psoriatic arthritis and in the last case, the patient suffered from HIV-associated psoriatic arthritis. The psoriatic arthritis was characterized as asymmetric chronic multiple-joint arthritis and was HLA B27 positive. The pathology of psoriatic arthritis was the accelerating bone turnover and ankylosis.

Symptomatic osteochondroma of the spine in elderly patients is extremely rare since it typically develops during skeletal growth. In this report, the authors show that pathological accelerating bone turnover such as psoriatic arthritis may be a possible mechanism for the onset of the enlargement of osteochondromas in elderly patients. The age of the patients in this report suggests that growth of the osteochondroma continues after skeletal development.

Psoriasis and osteoporosis: a sex-specific association?

Previous reports showed associations between psoriasis and chronic diseases. Little is known about the association between osteoporosis and psoriasis. The goal of the study was to assess the association between psoriasis and osteoporosis in a population-based case-control study, utilizing the database of a large health-care provider organization in Israel, Clalit Health Services. Patients (aged 51-90 years) diagnosed with psoriasis were compared with a sample of age- and sex-matched enrollees without psoriasis regarding the prevalence of osteoporosis. Data on health-related lifestyles and other comorbidities were collected. The study included 7,936 psoriasis cases and 14,835 controls. The prevalence of osteoporosis was significantly greater in males with psoriasis compared with the control group (3.1 vs 1.7%, P<0.001, odds ratio (OR)=1.86, 95% confidence interval (CI): 1.44-2.39) and slightly greater in females with psoriasis (22.3 vs 20.2%, P=0.008, OR=1.13, 95% CI: 1.03-1.25). A multivariate logistic regression model demonstrated that after controlling for confounders, psoriasis was significantly associated with osteoporosis in males (adjusted OR=1.70, 95% CI: 1.31-2.19, P<0.001). The weak association between psoriasis and osteoporosis in females lost statistical significance in a multivariate model (adjusted OR=1.09, 95% CI: 0.98-1.21, P=0.100). Psoriasis was found to be associated with osteoporosis among males, but not among females.

Erosive arthritis in a patient with pycnodysostosis: an experiment of nature

OBJECTIVE

The excellent poster painter Henri de Toulouse-Lautrec is the most famous patient with cathepsin K-deficient pycnodysostosis. Cathepsin K is believed to play a major role in osteoclast-driven bone resorption. In this study we explored the role of cathepsin K in bone resorption in a patient with a cathepsin K mutation causing pycnodysostosis in whom psoriatic arthritis also developed. We hypothesized that the patient would develop only inflammatory synovitis but would not develop bone erosions or other osteolytic changes.

METHODS

Monocytes from the patient with pycnodysostosis and normal control monocytes were isolated and stimulated to fuse and form multinuclear osteoclast-like cells, which were identified by evaluating messenger RNA expression of osteoclast markers. The ability to resorb bone was assessed by determining the extent of pit formation and levels of collagen degradation products generated by cathepsin K (C-terminal crosslinking telopeptide of type I collagen [CTX]) and matrix metalloproteinases (pyridinoline crosslinked C-terminal telopeptide of type I collagen). These experiments were also done in normal control cells after incubation with the cathepsin K inhibitor E64 during bone resorption.

RESULTS

In contrast to our a priori hypothesis, the patient developed a mutilating disease with extensive bony erosions associated with lysis of some of the distal phalanges of her hands and feet. After stimulation of monocytes from this patient, the cells formed multinuclear tartrate-resistant acid phosphatase-positive and calcitonin receptor-positive multikaryons, which, however, totally lacked cathepsin K. These multinuclear cells were able to resorb bone but, in contrast to normal control osteoclasts, did not produce CTX. The resorption pattern was abnormal in that, unlike normal control osteoclasts, both osteoclasts from the patient and E64-inhibited osteoclasts did not leave extensive osteoclast trails, but were relatively sessile.

CONCLUSION

In this "experiment of nature" we observed that cathepsin K is not necessary for bone degradation. These findings may be pertinent to our understanding of the functions of cathepsin K inhibitors, which are currently being developed as drugs to treat metabolic bone diseases.