The objective of this study is to evaluate the prevalence of
antiphospholipid antibodies, mainly anti-beta(2)-glycoprotein I (anti-beta(2)-GPI), and their possible clinical and laboratory relevance in
mixed connective tissue disease (
MCTD). This study included 39 consecutive patients with
MCTD (Kasukawa's criteria) from January, 2005, to March, 2007, and compared them with 21 age- and sex-matched healthy controls.
IgG and
IgM anticardiolipin (aCL) and anti-beta(2)-GPI were measured by ELISA.
Lupus anticoagulant (LA) was detected by functional coagulation tests. Medium to high titres of aCL and anti-beta(2)-GPI
antibodies were found in sera from four (10.2%)
MCTD patients. One of these patients was found to be positive for
IgM aCL,
IgM anti-beta(2)-GPI and LA
antibodies simultaneously. Additionally, this patient had a previous history of foetal loss in the second trimester and new-onset
pulmonary arterial hypertension (PAH). The other three patients had none of the manifestations of
antiphospholipid syndrome (APS) or PAH. The mean value of
IgG anti-beta(2)-GPI was higher among those
MCTD patients with PAH than in the group without PAH (34.2 +/- 46.8 vs 12.3 +/- 9.1, P = 0.018). None of the controls were positive for
antiphospholipid antibodies. High to moderate titres of anti-beta(2)-GPI as well as APS were rare in
MCTD, and these
antibodies may be correlated with the development of PAH in these patients.