Background: Systemic sclerosis (SSc) is a systemic inflammatory disease characterized by structural and functional abnormalities of small blood vessels, fibrosis of the skin and internal organs and activation of the immune system. The spectrum of clinical manifestations is wide, often including arthralgia and arthritis (30-60%), mucocutaneous symptoms and myopathy (20%), involvement of the kidneys (20%) and the gastrointestinal tract (diarrhea and malabsorption ). All of these manifestations can potentially influence bone metabolism.
Objectives: This study highlights the frequency of osteopenia and osteoporosis in 40 patients (35 women, 4 men, mean age: 54 yrs.) with systemic sclerosis (6 patients with diffuse SSc and 34 patients with limited SSc).
Methods: Bone mineral density (BMD) of the lumbar spine and the total left hip were measured by dual energy x-ray absorptiometry (DEXA; LUNAR Prodigy, GE Healthcare, Munich, Germany). Osteopenia and osteoporosis were diagnosed based on WHO criteria. In addition, the following laboratory and biochemical parameters were determined: osteocalcin, crosslaps, parathyroid hormone (PTH), calcium, 25- and 1.25-vitamin D, thyroid-stimulating hormone (TSH), erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP).
Results: Osteopenia was detected in 60% of patients (n = 24; 5 pat. with diffuse SSc, 19 pat. with limited SSc), osteoporosis in 30% (n = 12; 1 pat. with diffuse SSc, 11 pat. with limited SSc). Among the cases with osteoporosis we found 7 patients with 25-vitamin D deficiency (1 of these had also a 1.25-vitamin D deficiency despite normal kidney function). Osteocalcin levels were decreased in 2 patients, and creatinine was slightly elevated in 3 patients. Only 1 patient with osteoporosis presented a 25-vitamin D deficiency, and 2 patients had an moderately increased creatinine level. We found no significant correlation between the laboratory parameters and the BMD.

Conclusion: The data show that a decreased BMD is frequently present in SSc patients with osteopenia in 60% and osteoporosis in 30%, but there is no association with relevant laboratory parameters of bone metabolism. The results also support the need for evaluation of intermittent immobilisation, menopausal status, disease-related inflammatory activity and medication as potential factors for the reduction of BMD in SSc. However, the results of the vitamin D metabolites exclude osteomalacia or a reduced renal production of the biologically active D-hormone as an underlying cause. Therefore, a osteologic screening should be done routinely in patients with SSc to prevent loss of bone mass by early, adequate osteoprotective medication.