Acquired IgA deficiency.

During a prospective study of the ontogeny of the mucosal immune system using saliva, one subject acquired a selective IgA deficiency at 3 years 6 months of age. Prior to this time the infant had normal ontogeny patterns for salivary immunoglobulins and the salivary IgA was confirmed to be dimeric IgA containing secretory component. Two respiratory tract infections at 3 years 4 months and 3 years 5 months were reported prior to the collection of a saliva sample which was deficient in IgA. All subsequent saliva collections remained IgA deficient. Serum and saliva collected at 11 years of age confirmed persistent IgA deficiency. There was a family history of organ-specific autoimmune disease. The prospectively collected data indicate in this subject that the IgA deficiency was not congenital, but was acquired closely associated with two episodes of respiratory tract infections, against a genetic background of disturbed immune regulation.