The most frequent pathogenic gene variants associated with primary ciliary dyskinesia per country. There are clear regional differences between countries. The total absolute and relative frequency of the most frequent variant per country is shown in brackets. The variant c.2014C>T in SPAG1 (mint green) is the most frequently reported variant in Poland (24 out of 268 variants, 0.0896), the Czech Republic (12 out of 46 variants, 0.2609) and Slovakia (10 out of 16 variants, 0.625). The variant c.742G>A in ODAD1 (pale pink) prevails in the Netherlands. The variant c.248_252dup in CCNO (yellow) is the most frequently detected variant in Turkey and c.248del in CCDC40 (dark green) is the most frequently detected variant in Denmark (17 out of 182 variants, 0.0934), Norway (9 out of 80 variants, 0.1125) and Belgium (5 out of 64 variants, 0.0781). Despite the overall high involvement of DNAH5 (figure 1), none of its variants was identified as the most frequent in any of the countries. Argentina and Brazil are not shown (no most frequent genetic variant).