Antiphospholipid syndrome (APS) can occur in patients without an underlying systemic autoimmune disease (primary APS) or with other autoimmune disease (previously known as secondary APS), particularly in association with systemic lupus erythematosus (SLE). The annual incidence of APS in adults has been reported to be 2 per 100,000 population, while the estimated prevalence is 50 per 100,000.[5]Duarte-García A, Pham MM, Crowson CS, et al. The epidemiology of antiphospholipid syndrome: a population-based study. Arthritis Rheumatol. 2019 Sep;71(9):1545-52.
http://www.ncbi.nlm.nih.gov/pubmed/30957430?tool=bestpractice.com
Antiphospholipid antibodies have been reported to have a prevalence of between 1.0% and 5.6% in normal healthy populations and may increase with age.[6]Shi W, Krilis SA, Chong BH, et al. Prevalence of lupus anticoagulant and anticardiolipin antibodies in a healthy population. Aust N Z J Med. 1990 Jun;20(3):231-6.
http://www.ncbi.nlm.nih.gov/pubmed/2115326?tool=bestpractice.com
[7]Petri M. Epidemiology of the antiphospholipid antibody syndrome. J Autoimmun. 2000 Sep;15(2):145-51.
http://www.ncbi.nlm.nih.gov/pubmed/10968901?tool=bestpractice.com
The prevalence of antiphospholipid antibodies in association with SLE has been shown to be 30% to 40%, and 6% with rheumatoid arthritis.[8]Lim W, Crowther MA, Eikelboom JW. Management of antiphospholipid antibody syndrome: a systematic review. JAMA. 2006 Mar 1;295(9):1050-7.
http://jama.ama-assn.org/cgi/content/full/295/9/1050
http://www.ncbi.nlm.nih.gov/pubmed/16507806?tool=bestpractice.com
Antiphospholipid antibodies have been reported in up to 14% of patients presenting with thrombosis and in 20% of patients presenting with recurrent pregnancy losses.[8]Lim W, Crowther MA, Eikelboom JW. Management of antiphospholipid antibody syndrome: a systematic review. JAMA. 2006 Mar 1;295(9):1050-7.
http://jama.ama-assn.org/cgi/content/full/295/9/1050
http://www.ncbi.nlm.nih.gov/pubmed/16507806?tool=bestpractice.com
[9]Erkan D, Lockshin MD. What is antiphospholipid syndrome? Curr Rheumatol Rep. 2004 Dec;6(6):451-7.
http://www.ncbi.nlm.nih.gov/pubmed/15527704?tool=bestpractice.com
[10]Rai RS, Regan L, Clifford K, et al. Antiphospholipid antibodies and beta 2-glycoprotein-I in 500 women with recurrent miscarriage: results of a comprehensive screening approach. Hum Reprod. 1995 Aug;10(8):2001-5.
http://www.ncbi.nlm.nih.gov/pubmed/8567830?tool=bestpractice.com
[11]Loizou S, Byron MA, Englert HJ, et al. Association of quantitative anticardiolipin antibody levels with fetal loss and time of loss in systemic lupus erythematosus. Q J Med. 1988 Jul;68(255):525-31.
http://www.ncbi.nlm.nih.gov/pubmed/3252304?tool=bestpractice.com
Female-to-male ratios ranging from 5:1 to 2:1 have also been observed.[12]Jara LJ, Medina G, Vera-Lastra O, et al. The impact of gender on clinical manifestations of primary antiphospholipid syndrome. Lupus. 2005;14(8):607-12.
http://www.ncbi.nlm.nih.gov/pubmed/16175932?tool=bestpractice.com
The mean age of symptom onset is approximately 34 years, with 85% of patients being diagnosed between ages 15 and 50 years.[12]Jara LJ, Medina G, Vera-Lastra O, et al. The impact of gender on clinical manifestations of primary antiphospholipid syndrome. Lupus. 2005;14(8):607-12.
http://www.ncbi.nlm.nih.gov/pubmed/16175932?tool=bestpractice.com