BACKGROUND IgA deficiency (IGAD) is the most common primary antibody deficiency. Although many affected individuals have no apparent symptom, selected patients suffer from recurrent mucosal infections, allergies, and autoimmune diseases. We aimed to investigate the clinical features in relation to immune function of Iranian patients with symptomatic IGAD. METHODS Thirty-seven patients (21 male and 16 female), aged 4-32 years, were evaluated in this study. Patients were followed for a total of 131 patient years with a mean follow-up of 3.5 years per patient. RESULTS The most prevalent presentations were recurrent infections occurring in 27 subjects, followed by allergy in eight cases and autoimmunity in two patients. However, during the follow-up period, 35 patients developed infections in respiratory and gastrointestinal tracts, necessitating medical care. Apart from infections, allergy was the most frequent complaint (31 cases); the major features were asthma, atopic dermatitis, and allergic rhinoconjunctivitis. Autoimmune diseases were documented in ten cases; thyroiditis was the most common. In 31 patients who received unconjugated pneumococcal polyvalent vaccine, antibody response against polysaccharide antigen was measured before and 28 days after vaccination. One fourth of vaccinated patients were hyporesponsive to vaccine; four of these patients developed bronchiectasis. The patients with IGAD were classified into two groups: group 1 (14 cases) consisted of patients with IGAD and other associated immune defects, such as immunoglobulin G (IgG) subclass deficiency and defective specific antibody production. Group 2 (23 cases) had isolated IGAD without other immunological abnormalities. There was a significantly increased number of lower respiratory tract infections in group 1 compared with group 2 (P = 0.006). Moreover, four patients of group 1 had bronchiectasis whereas none of the patients in group 2 developed this complication (P = 0.015). CONCLUSIONS Subclassification of IGAD regarding the existence of associated immune defects is useful in terms of morbidity and planning for medical care. IgA-deficient patients with concomitant immune defects such as defects in specific antibody production have higher rates of recurrent infections and bronchiectasis, which necessitates more effective monitoring.