Distribution of primary immunodeficiency diseases in the Turk ethnic group, living in the northwestern Iran.

Primary immunodeficiency disorders (PID) are a heterogeneous group of disorders, characterized by an unusual increased susceptibility to various infections. In order to study the frequency of PID in Turk ethnic group of northwestern Iran, this study was performed. Fifty-nine PID patients (36 male and 23 female) with a mean age of 5.3 years (median: 3 years; range: <1 to 22 years) were diagnosed in a 5-year period. The estimated occurrence of PID is about 24 per 100,000 live births in this region. Combined T- and B-cell immunodeficiencies were the most common form of PID in this region, including severe combined immunodeficiency (32.2%), followed by ataxia-telangiectasia (22.0%) and common variable immunodeficiency (18.6%). Recurrent infections were found in almost all our patients, particularly in the respiratory and gastrointestinal systems. Fifteen patients died (25.4%) because of recurrent and severe infections. All dead patients belong to the group of combined T- and B-cell immunodeficiencies. Although PID was previously considered as a group of rare disorders, these is an increased trend in recognition of PID. The high incidence of severe combined immunodeficiency and ataxia-telangiectasia could be due to the genetic backgrounds in the Turk ethnic group.