Overall, we detected ultrastructural hallmark (class 1) defects in six patients with probable PCD and inconclusive WES results due to VUS in the established PCD genes CCDC40 (n = 3; Figure 1), CCDC103, DNAH5, and DNAI1 (n = 1, each; Figure 2). Here, DNAI1 is linked to primary ciliary dyskinesia.