Distribution of primary immunodeficiency diseases diagnosed in a pediatric tertiary hospital

Background: Advances in immunologic techniques in recent years have led to increased recognition of primary immunodeficiency disorders, with IgA deficiency the most common phenotype reported by most registries. There have also been reports of increased associated incidence of autoimmunity, allergy, and other diseases. Objectives: We wished to determine the percentage of different primary immunodeficiency disorders seen in a pediatric tertiary hospital and to determine the association of primary immunodeficiency disorders with other diseases that are not part of classic immunodeficiency disorders. Methods: We performed a retrospective review of the patients referred to our allergy/immunology clinic for immunologic evaluation of recurrent infections during an 8-year period. We also reviewed pathology reports with postmortem diagnosis of immunodeficiencies not identified while patients were alive. Results: Of the 91 patients with primary immunodeficiency disorders evaluated, the majority had predominantly antibody deficiencies (67%). The most common phenotype was specific antibody deficiency with normal immunoglobulins (23.1%), defined as inability to mount an adequate response to pneumococcal polysaccharides followed by IgG2 subclass deficiency (17.6%). These two phenotypes were diagnosed mostly in the last 2 years of the survey. Associated diseases, found in 40% of patients, were mostly allergic conditions followed by syndromic/chromosomal disorders. Conclusion: The study reveals that specific antibody deficiency with normal immunoglobulins followed by IgG2 subclass deficiency was the most frequently diagnosed primary immunodeficiency disorder in our patient population. It also indicates that immunodeficiency disorders should be considered in patients with other abnormalities like allergic and syndromic/chromosomal disorders that present with recurrent infections.