What is Primary Ciliary Dyskinesia (PCD)
PCD stands for primary ciliary dyskinesia, an inherited disorder of motile (moving) cilia. PCD is also sometimes referred to as Kartagener syndrome (PCD with situs inversus) or immotile cilia syndrome.
Effective activity of motile cilia is required to keep the lungs, sinuses and ears free of unwanted organisms and debris that can cause infection and disease. Motile cilia also are important in helping determine organ placement in the developing embryo and in moving the cells of reproduction into place (sperm tails in males with PCD may also be immotile and egg cells in females with PCD may have impaired motility because the fallopian tubes through which they travel rely on ciliary activity). Motile cilia are also found in the ventricles of the brain and in rare cases, hydrocephalus (excess fluid in brain ventricles due to impaired fluid flow) may be associated with PCD.
A person with PCD experiences chronic, recurrent infections in the lungs, ears and sinuses due to the loss of ciliary activity in those areas. Faulty determination of organ placement (aka ‘situs’) may result in reversed organs or in other organ placement/development abnormalities. Reduced sperm motility means that most males with PCD are infertile (not sterile—the sperm are still viable, they just can’t get where they need to be) and women with PCD may experience subfertility or increased risk for miscarriage or ectopic pregnancy. Some women with PCD are able to conceive with no problems.
How do people get PCD?
PCD is a genetic disorder, meaning it is inherited from one’s parents and cannot be acquired from the environment. PCD is most often passed on in what is called an ‘autosomal recessive’ pattern of inheritance, in which the disease is only expressed when a child inherits two copies of a mutated gene—one from each parent. The parents are considered ‘carriers’ because they ‘carry’ the mutation, but are not sick themselves because they only have one copy of the mutated gene. When two carriers produce children, however, they have a 1 in 4 (25%) chance of having a child who will inherit both of their mutations, which will result in the disease being expressed.
One common misconception with PCD is that since it is inherited, it should be seen in other family members. Recessive diseases simply don’t work in that way. Carrier status can be unknowingly passed in a family for decades, possibly even centuries, before a carrier meets another carrier by random chance and they produce an affected child. Because there is a 1 in 4 chance (with each pregnancy, not with the total number of children produced) of passing a recessive disease, it is not uncommon to see family groups with multiple affected siblings. It is not common, however, for PCD to pass fromparent to child to aunt to cousin, etc. This form of inheritance suggests thatsomething other than a recessive trait is at work.
Because we don’t know everything about PCD genetics at this point, suspicion of PCD requires diligent workup from PCD experts to make sure that the diagnosis has not been made in error.
For more information on autosomal recessive inheritance: