Bone mineral density in patients with psoriatic arthritis

Little information is available concerning bone mass in patients with psoriatic arthritis (PsA): the existence of less severe periarticular osteoporosis is considered possible, but there are no data concerning the existence of systemic osteoporosis. We investigated bone mineral density (BMD) in patients with PsA.

We studied 186 patients with non-axial PsA and 100 healthy subjects, equally divided into 3 groups: women of child-bearing age, women in menopause, and men. No patient had previously received steroid treatment. In all patients, evaluation was made of disease duration, inflammation indices (erythrocyte sedimentation rate, C-reactive protein), functional indices (Steinbrocker scale), and the Health Assessment Questionnaire (HAQ). BMD was measured by fan-beam x-ray densitometry of the lumbar spine, femur, and total body (evaluating the whole skeleton, as well as the spine, trunk, and upper and lower limbs). Ultrasound densitometry of the heel was also performed.

BMD was significantly lower in the arthritic than in the healthy subjects regardless of sex, menopausal status, or age, as expressed in g/cm2 (lumbar spine 1.112 vs 1.326; femoral neck 0.870 vs 1.006; total body 1.125 vs 1.203) or by T and Z scores (lumbar T = -1.36, Z = -0.98; femoral neck T = -1.12, Z = -0.83; total body T = -1.09, Z = -0.65). Ultrasound densitometry of the heel was similarly altered (stiffness 96 vs 77; T -1.78; Z -1.29). Among the PsA patients, demineralization in at least one skeletal region was observed in 67% of premenopausal women (marked in 11%), 100% of postmenopausal women (marked in 47%), and 80% of the men (marked in 29%). In premenopausal women, demineralization did not correlate with the disease variables; in postmenopausal women and the men, it correlated with a decline in the functional indices and the HAQ score. This was confirmed by analysis of the relative risk of osteoporosis expressed in odds ratios (HAQ: 1.6; age: 1.4; years since menopause: 1.7).

Demineralization was observed in more than 2/3 of our PsA patients without axial involvement. This demineralization was not related to the indices of inflammation or disease duration, but there is a delayed correlation with HAQ score, as well as age and the number of years since menopause.