Background Systemic lupus erythematosus (SLE) patients are prone to osteoporosis and fracture due to disease itself and its therapies. Many studies of bone quality have involved in patients with adult-onset SLE (a-SLE), but only a few have concerned childhood-onset SLE (c-SLE) patients, who were at special risk of loss of bone mass. This is because they have developed the disease before achieving peak bone mass, which was reached in late teens or early adulthood after a gradual increase of bone mass throughout childhood and adolescence. Lilleby reported a high prevalence of osteopenia (41%) in young patients with a history of c-SLE. However the information of the alterations of bone quality in this kind of patients is still scant.
Objectives To study alterations of bone geometry, density and microarchitecture in women with SLE on long-term GCs according to disease onset.
Methods 179 Chinese women with SLE who were receiving prednisone at least 5 mg/d for at least 1 year before study entry were selected, among whom, 18 were c-SLE (diagnostic age <18 years), 161 were a-SLE (diagnostic age ≥18 years). aBMD at femoral neck, total hip and lumbar spine were measured by DXA. Bone microarchitecture at the non-dominant distal radius was measured by high-resolution peripheral quantitative CT (HR-pQCT) and bone mechanical properties were analyzed by finite element (FE).
Results Compared with a-SLE patients, patients with c-SLE were significantly younger (28yr vs.44yr), with longer GCs duration (14yr vs.11yr). All of the c-SLE patients were premenopausal, while 69 (42.9%) a-SLE patients were postmenopausal. NPLE, musculoskeletal damage and photosensitivity were more common in c-SLE patients, but no significant difference was in the prevalence of other clinical manifestations, such as nephritis or renal damage. Although aBMD at all measured sites were not significantly different between two groups, osteopenia and osteoporosis at either one site was more common in c-SLE than a-SLE (56% vs. 44%). Measured by HR-pQCT and FE, significantly lower cortical bone area (p<0.001), density (p=0.004) and thickness (p=0.003), smaller trabecular separation (p<0.001), more trabecular number (p=0.003), lower bone stiffness (p=0.03) and failure load (p=0.05) were detected in c-SLE patients. Lower cortical area, density, thickness, bone stiffness and failure load persisted in c-SLE patients even after adjusted for age, menstrual status, body mass index, duration of GCs use, highest GCs dose, disease duration, total and mean SLEDAI, disease damage (SDI), smoking, alcohol drinking, physical activities and diabetes.
Conclusions C-SLE is an independent risk factor for deterioration of bone microarchitecture and mechanical properties. Early use of GCs-sparing therapies which may preserve bone quality should be applied on c-SLE patients.
Matkovic V, Jelic T, et al. Timing of peak bone mass in Caucasian females and its implication for the prevention of osteoporosis. Inference from a cross-sectional model. J Clin Invest 1994;93:799-808.
Lilleby V, Lien G, et al. Frequency of osteopenia in children and young adults with childhood-onset systemic lupus erythematosus. Arthritis Rheum 2005;52:2051-9.
Disclosure of Interest None Declared