Transmission Electron Microscopy in the Diagnosis of Primary Ciliary Dyskinesia

Abstract

Primary ciliary dyskinesia (PCD) is an autosomal recessive disease with extensivegenetic heterogeneity. Dyskinetic or completely absent motility of cilia predisposesto recurrent pulmonary and upper respiratory tract infections resulting in bronchiec-tasis. Also infections of the middle ear are common due to lack of ciliary movementin the Eustachian tube. Men have reduced fertility due to spermatozoa with absentmotility or abnormalities in the ductuli efferentes. Female subfertility and tendencyto ectopic pregnancy has also been suggested. Headache, a common complaint inPCD patients, has been associated with absence of cilia in the brain ventricles, lead-ing to decreased circulation of the cerebrospinal fluid.

Finally, half of the patients with PCD has situs inversus, probably due to the absence of ciliary motility inHensen's node in the embryo, which is responsible for the unidirectional flow offluid on the back of the embryo, which determines sidedness. PCD, which is aninborn disease, should be distinguished from secondary ciliary dyskinesia (SCD)which is an acquired disease. Transmission electron microscopy is the most com-monly used method for diagnosis of PCD, even though alternative methods, such asdetermination of ciliary motility and measurement of exhaled nitric oxide (NO) maybe considered.

The best method to distinguish PCD from SCD is the determination of the number of inner and outer dynein arms, which can be carried out reliably on alimited number of ciliary cross-sections. There is also a significant difference in theciliary orientation (determined by the direction of a line drawn through the centralmicrotubule pair) between PCD and SCD, but there is some overlap in the values, making this parameter less suitable to distinguish PCD from SCD.