Background Rheumatoid (RA) and psoriatic (PsA) arthritis are chronic diseases characterized by inflammation, often common therapies and prolonged joint immobilization are possible risk factors of bone loss and fragility fractures.1 Vitamin D is a key regulator of calcium homeostasis and skeletal health, but also seem to play an important role as risk factor for RA and PsA
Objectives to determine bone mineral density (BMD) and 25-dihydroxyvitaminD3 [25(OH)D3 ] serum concentrationin RA and PsA patients
Methods The study included 61 postmenopausal patients (mean age 65±8 years) affected by RA, 45 PSA symmetrical type (mean age 63±4 years) and 31 age-matched healthy controls. BMD at the lumbar spine (L1-L4) and at the proximal femur was analyzed using dual-energy X-ray absorptiometry (DXA) scan (Lunar Prodigy, GE, USA). The results of BMD were expressed in g/cm2 and the diagnosis of osteoporosis was defined according to WHO guidelines as T-score less -2.5 whereas osteopenia as T-score between -1.0 and -2.5 at any site. Laboratory assessment included quantitative determination of 25(OH)D3 concentration performed by DiaSorin radioimmunoassay kit and the cut-off defined according to international guidelines2.
Results Among the 45 patients with PsA, 5 (11%) presented osteoporosis and 15 (33%) osteopenia. Fifteen RA patients(25%) showed an osteoporotic condition and 14 (23%) an osteopenic status. BMD, T and Z scores at lumbar spine and at all site of femur were found significantly lower in RA and PsA patients than in control group. 25(OH)D3concentration were (RA: 13.9±8.0 ng/mL vs PsA: 15.9±7.4 ng/mL vs 44.8±4.7 ng/mL p<0.001). BMD was significantly lower in the RA than in PsA patients (femoral neck: BMD 0.781±0.11 g/cm2 vs 0.823±0.10 g/cm2 p=0.02; ward: BMD 0.582±0.13 g/cm2 vs 0.663±0.11 g/cm2 p=0.02; trocanther: BMD 0.668±0.13 g/cm2 vs 0.714±0.08 g/cm2 p=0.01). Similarly, the T-score value in all site determined were lower in RA versus PsA patients (femoral neck: -1.6 ±1.0 vs-1.2±0.88 p=0.01; ward:-2.4 ±1.0 vs -1.9±0.9 p=0.02; trocanther: - 1.1 ±1.2 vs -0.8± 0.8 p=0.03; total hip: T-score -1.4±1.2 vs-0.88±1.0 p=0.03). A significant positive correlation was found between T and Z scores at lumbar spine in RA and 25(OH)D3concentration (r=0.28 p=0.02 and r=0.27 p=0.03); as well in PsA group 25(OH)D3 was related to BMD, T-score and Z-score at all site of evaluation of femur. (Femoral neck BMD: r=0.69 p<0.001, T-score: r=0.68 p<0.001, Z-score: r=0.63 p<0.001; Ward BMD r=0.54 p=0.001, T-score:r=0.54 p=0.001, Z-score: r=0.54 p<0.001; Trocanther: BMD: r=0.42 p=0.03; T-score: r=0.59 p<0.001, Z-score:r=0.42 p=0.003;Total hip: BMD:r=0.67 p<0.001, T-score: r=0.52 p=0.002)
Conclusions This study reports that bone loss occurs both in RA and in PsA patients, but overall BMD decrease was less evident in PsA patients. In both diseases insufficient/deficient levels of vitamin D are correlated with BMD decrease. The most intensive chronic inflammation in RA patients might partially explain their most evident systemic bone loss versus PsA patients.
Simeon Grazio et al. Osteoporosis in psoriatic arthritis:is there any? Wien Klin Wochenschr 2001;123:743-750
Holick MF. Vitamin D deficiency. N.Engl J Med 2007;357:266-281
Disclosure of Interest None Declared