To evaluate the association between keratoconus (KC) and immune disorders (IDs).
A retrospective observational case-control study of all the members in the Central District of Clalit Health Services in Israel who were diagnosed to have KC (years 2000-2007; n = 426) and 1704 age- and gender-matched controls. We calculated the prevalence of the following IDs: rheumatoid arthritis, ulcerative colitis, arthropathy, amyloidosis, systemic lupus erythematosus, celiac disease, multiple sclerosis, myasthenia gravis, polymyalgia rheumatica, idiopathic thrombocytopenic purpura, Crohn disease, Hashimoto thyroiditis, autoimmune hepatitis, irritable bowel syndrome, asthma, and environmental allergy. The odds ratio (OR) of having IDs among patients with KC was compared with controls.
The association between KC and the following IDs was statistically significant: rheumatoid arthritis [OR = 8.1; 95% (confidence interval) CI: 1.5-44.2], ulcerative colitis (OR = 12.1; CI: 1.3-116), autoimmune chronic active hepatitis (OR = 6; CI: 1.01-36), Hashimoto thyroiditis (OR = 2.0; CI: 1.2-3.3), arthropathy (OR = 1.4; CI: 1.1-1.8), asthma (OR = 2.1; CI: 1.4-3.2), environmental allergy (OR = 1.3; CI: 1.02-1.75), and irritable bowel syndrome (OR = 5; CI: 2.1-12.1). Two autoimmune diseases, multiple sclerosis (OR = 2; CI: 0.2-22) and Crohn disease (OR = 1.6; CI: 0.3-8.3), were more prevalent among patients with KC but did not reach statistical significance.
Some strong associations between KC and several immune conditions of autoimmune diseases and allergic IDs may point to the role of the immune system in the pathogenesis of KC.