Background: Eleven years ago we had described three patients with missing nexin links as a possible cause of primary ciliary dyskinesia (PCD). The assumption was substantiated last year by finding a mutation in these patients.
Materials and methods: We counted the nexin links, inner (IDA) and outer (ODA) dynein arms and microtubuli in each of, if possible, 50 cilia in 41 patients with normal cilia, 4 patients with deficiency of nexin links only and 4 with deficiency of nexin links and IDA.
Results: In the control group the median number of nexin links was 4.5 per cilium, range 3.4-5.3. In the second group the mean numbers of nexin links per cilium were 1.1-1.4, in the third group 0.8-1.2, per patient. The median number of IDA was in the control group 4.2, range 3.3-5.2. In groups 2 and 3 the numbers were 3.0-3.5 and 0.2-1.0, respectively. Numbers of ODA were normal in all groups.
Conclusions: It is possible to reliable count the number of nexin links in nasal human cilia and to distinguish cases with missing nexin links from normal controls.
Keywords: Electron microscopy; inner dynein arms; nasal cilium; nexin links; primary ciliary dyskinesia.