title: Primary immunodeficiency diseases worldwide: more common than generally thought.
abstract: OBJECTIVE
  Primary immunodeficiency diseases (PIDs) comprise at least 176 hereditary disorders that are thought to be individually and collectively rare. The actual prevalence and incidence of PIDs remains unclear, but recent epidemiologic studies have suggested that PIDs are more common than generally thought. Based on these studies, we attempted to estimate the worldwide prevalence and incidence of PIDs.
  
  
  METHODS
  Using data from registries and two recent epidemiologic surveys estimating the frequencies of PIDs, we extrapolated the frequencies reported for certain countries to the populations of continents and of the world.
  
  
  RESULTS
  Our upper estimates suggest that six million people may be living with a PID worldwide, whereas only 27,000-60,000 have been identified to date (all national registries and the Jeffrey Modell Centers Network, respectively). For Europe, our upper estimate was 638,000 cases, and 15,052 cases are currently registered (2.27 %). In Africa, up to 902,631 people may have a PID, whereas only 1,016 cases are currently registered. We also found that PIDs were prevalent not only in children, but also in adults, who were strongly underrepresented in registries.
  
  
  CONCLUSIONS
  Specific, dedicated epidemiologic studies are required, to obtain more realistic statistics for PIDs and to increase the awareness of physicians and public health systems about these diseases. Furthermore, the field of PIDs is continually growing, and this is likely to lead to a revision of the definition of these conditions, potentially increasing estimates of their impact on both adults and children, at the population level.
authors: Clinical Immunology Unit, King Hassan II University, Averroes Hospital, Casablanca, Morocco. profbousfiha@gmail.com
authors: Ahmed Aziz
authors: AA
authors: Bousfiha
authors: Leïla
authors: L
authors: Jeddane
authors: Fatima
authors: F
authors: Ailal
authors: Ibtihal
authors: I
authors: Benhsaien
authors: Nizar
authors: N
authors: Mahlaoui
authors: Jean-Laurent
authors: JL
authors: Casanova
authors: Laurent
authors: L
authors: Abel
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D017074:Common Variable Immunodeficiency / Q000453:epidemiology* / Q000276:immunology* / Q000628:therapy; D006105:Granulomatous Disease, Chronic / Q000453:epidemiology / Q000276:immunology / Q000628:therapy; D006801:Humans; D007223:Infant; D011788:Quality of Life; D011795:Surveys and Questionnaires