Please cite this article in press as: Mohammadzadeh I, et al. Primary immunodeficiency diseases in Northern Iran. Allergol Immunopathol (Madr). 2017. http://dx.doi.org/10.1016/j.aller.2016.11.001 ARTICLE IN PRESS +Model ALLER-832; No. of Pages 7 Allergol Immunopathol (Madr). 2017;xxx(xx):xxx---xxx www.elsevier.es/ai Allergologia et immunopathologia Sociedad Espa ˜ nola de Inmunolog´ ıa Cl´ ınica, Alergolog´ ıa y Asma Pedi ´ atrica ORIGINAL ARTICLE Primary immunodeficiency diseases in Northern Iran I. Mohammadzadeh a,b , B. Moazzami a,b , J. Ghaffari c , A. Aghamohammadi d,e , N. Rezaei d,f,g,* a Noncommunicable Pediatric Diseases Research Center, Babol University of Medical Sciences, Babol, Iran b Primary Immunodeficiency Diseases Network (PIDNet), Universal Scientific Education and Research Network (USERN), Babol, Iran c Department of Pediatrics, School of Medicine, Mazandaran University of Medical Sciences, Sari, Iran d Research Center for Immunodeficiencies, Children’s Medical Center, Tehran University of Medical Sciences, Tehran, Iran e Primary Immunodeficiency Diseases Network (PIDNet), Universal Scientific Education and Research Network (USERN), Tehran, Iran f Department of Immunology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran g Network of Immunity in Infection, Malignancy and Autoimmunity (NIIMA), Universal Scientific Education and Research Network (USERN), Boston, MA, USA Received 18 June 2016; accepted 1 November 2016 KEYWORDS Primary immunodeficiency diseases; Hypogammaglobulinaemia; Phagocyte defects; Combined immunodeficiencies; Frequency Abstract Introduction: Primary immunodeficiency diseases (PID) are a heterogeneous group of inherited disorders, characterised by recurrent severe infections, autoimmunity and lymphoproliferation. Despite impressive progress in identification of novel PID, there is an unfortunate lack of aware- ness among physicians in identification of patients with PID, especially in non-capital cities of countries worldwide. Result: This study was performed in a single-centre paediatric hospital in Northern Iran during a 21-year period (1994---2015). Ninety-four patients were included in this study. The majority of cases had antibody deficiencies (37.23%), followed by well-defined syndromes with immunode- ficiency in 16 (17.02%), phagocytic disorders in 15 patients (15.95%), complement deficiencies in 15 patients (15.95%), immunodeficiencies affecting cellular and humoral immunity in nine patients (9.57%), disease of immune dysregulation in three (3.19%), and defects in intrinsic and innate immunity in one (1.06%). Conclusion: It seems that there are major variations in frequency of different types of PID in different regions of a country. Therefore, reporting local data could provide better ideas to improve the local health care system strategists and quality of care of PID patients. © 2017 SEICAP. Published by Elsevier Espa˜ na, S.L.U. All rights reserved. ∗ Corresponding author. E-mail address: rezaei nima@tums.ac.ir (N. Rezaei). http://dx.doi.org/10.1016/j.aller.2016.11.001 0301-0546/© 2017 SEICAP. Published by Elsevier Espa˜ na, S.L.U. All rights reserved.