Selective immunoglobulin A deficiency and celiac disease: let's give serology a chance.

Patients with selective immunoglobulin (Ig) A deficiency have a 10- to 20-fold increased risk of celiac disease. In these patients, serological diagnosis of celiac disease can be difficult, since specific IgA-based assays are usually negative and IgG-specific antibody tests are insufficiently reliable. We describe a girl with selective IgA deficiency who had a troublesome diagnosis of celiac disease that was established only after an unexpected positive test result for antitransglutaminase IgA and antiendomysium IgA. Our observation indicates that IgA-based serology should not be forgotten in patients with selective IgA deficiency, since positive results for antitransglutaminase IgA, antiendomysium IgA, or both can be observed at any time during diagnostic investigations.