Background/Purpose: Systemic Sclerosis (SSc) is an autoimmune disease characterized by collagen deposition and vascular changes of the skin and internal organs, leading ultimately to fibrosis.   Antiphospholipid (aPL) antibodies are immunoglobulins directed against negatively charged phospholipid-binding proteins mostly involved in blood coagulation.  It has been suggested that aPL antibodies including anticardiolipin (aCL) and anti-beta-2-glycoprotein I (aβ2GPI) antibodies may play a role in the pathogenesis of SSc related vascular impairment. This study investigates the prevalence of antiphospholipid antibodies including aCL and aβ2GPI antibodies in patients with systemic sclerosis.  We also evaluated a possible relationship between clinical findings in SSc including Raynaud’s phenomenon, digital ulcers, and interstitial lung disease, and the presence of aCL/ aβ2GPI antibodies. 

Methods:  A hundred patients who met the American College of Rheumatology classification criteria for systemic sclerosis were included in the study.  There were ten men and ninety women with a median age of 58 years.  Thirty-five percent had diffuse cutaneous SSc and 65 percent had limited cutaneous SSc.   Assessment of organ involvement to detect systemic complications of SSc included presence of Rayanud’s phenomenon, digital ulcers or pitting scars, and interstitial lung disease.  Interstitial lung disease was characterized by pulmonary fibrosis seen on high-resolution computed tomography or chest radiography, or occurrence of “velcro” crackles on auscultation, not due to another cause such as congestive heart failure.  Anticardiolipin IgG, IgM, and IgA and anti-beta-2-glycoprotein I IgG, IgM, and IgA antibodies were measured by enzyme-linked immunosorbent assay.  Clinical associations were measured using conditional and simple logistic regression models. 

Results: Twenty-seven percent of patients with systemic sclerosis were positive for either anticardiolipin or anti-beta-2-glycoprotein I (aβ2GPI) antibodies.  A positive association was found between the presence of anticardiolipin antibody and interstitial lung disease (p=0.038).  This association was maintained after adjusting for age, sex, and race (OR 2.765, 95% CI 1.038-7.368, p=0.0412). Anticardiolipin testing was not sensitive for predicting lung involvement with a sensitivity of 0.419, however, it had a high specificity at 0.789 for predicting lung involvement.  There was no predictive value found for testing aCL and aβ2GPI antibodies with regards to Raynaud’s phenomenon or digital ulcers. 

Conclusion: Our study showed a positive association with aCL antibodies and interstitial lung disease in patients with systemic sclerosis.  The use of aCL antibodies as a biomarker of pulmonary disease in SSc should be further explored.

 Table 1. Association of positive anticardiolipin and anti-beta-2-glycoprotein I antibody testing with clinical features in SSc patients.