Acquired ciliary defects compared to those seen in the immotile-cilia syndrome.

An attempt is made to characterize injured cilia and ciliary mutants separately with particular emphasis on human conditions. The usefulness of electron microscopical investigations is stressed. An injury to a ciliated epithelium may very well be restricted to one site in the body and may appear at any stage of life. Typical ciliary mutants, such as are seen in the immotile-cilia syndrome, represent a generalized condition and will be found from the beginning of life. Some types of ciliary defects are relatively unspecific and found after various kinds of insult to the cilia also in the immotile-cilia syndrome; these are: compound cilia, supernumerary microtubules in the axoneme, and loss of cilia or of ciliated cells. Other kinds of ciliary defect seem to be typical of the ciliary mutants: absence of dynein arms, absence of spokes and central sheath, transposition of one of the central microtubules and short central microtubules.