However, TEM should not be used in isolation to exclude a PCD diagnosis, because standardized protocols and consensus on terminology, especially regarding the number and proportion of cilia required to make a diagnosis, are lacking and 15–30% of patients with PCD have apparently normal ciliary ultrastructure, for example those with a pathogenic variant in DNAH11 [36, 54]. Here, DNAH11 is linked to primary ciliary dyskinesia.