CP and primary ciliary dyskinesia: Mutations in RSPH1 [9], RSPH4A [10], RSPH9 [10], RSPH3 [11], DNAJB13 [12], and RSPH23/NME5 [13,14] cause radial spoke and/or ciliary central pair (CP) defects, which together with situs solitus account for a large proportion of PCD cases presenting with radial spoke (RS) and CP-associated defects [11].