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Canine Primary Ciliary Dyskinesia (PCD)
| Acronym: | PCD |
| Gene: | CCDC39 |
| Mutation: | c.286C>T |
| Inheritance: | Autosomal recessive |
| Sample type: | CHS (Cheek Swab), WBE (Whole Blood EDTA) |
Genetics and characteristics
Dog Primary Ciliary Dyskinesia (PCD) is an inherited disorder that causes defects in the upper and lower respiratory tract, as well as in the flagella of sperm cells, causing infertility. Previously it was known as immotile cilia syndrome (ICS). Until now, primary ciliary dyskinesia has been identified in more than 19 breeds, such as Border collies, Bull Mastiffs, Chihuahuas, Shar peis, Chow chows, etc. However, the causative mutation has so far been identified only in the Bobtail dog breed. A cilium is an organelle found in eukaryotic cells. Cilia cells that are in the lining of the trachea have an important role in sweeping mucus and dirt out of the lungs. When the ciliary function becomes ineffective, it results in poor mucus clearance from the airways. This with time results in chronic mucus plugging and inflammation of nasal cavities, trachea, and lower airways. Progressively this can lead to rhinosinusitis, bronchitis, bronchopneumonia, and bronchiectasis, all known as chronic respiratory abnormalities. Other than that, other known clinical signs are bilateral mucopurulent nasal discharge, hyperpnea, increased upper airway sounds, orthopnea, and cyanosis. Symptoms occur at an early age, which is already in few weeks or months after the cub’s birth. Exceptional cases of affected dogs that remained asymptomatic for prolonged periods have been reported. These dogs remained asymptomatic from six months to ten years.
Dog Primary Ciliary Dyskinesia (PCD) is inherited as an autosomal recessive disorder. A dog carrying one copy of the mutated gene is heterozygous and will not show the PCD symptoms. When mating two carriers (heterozygotes) at conception each cub has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Currently, there is no cure for PCD and the only way to avoid obtaining affected cubs is to breed dogs that are not carriers of the mutation. Defected genes for autosomal recessive disease can be passed for many generations without affected individuals occurring until two carriers are bred to one another. The only way to find out if there is a chance of getting an affected puppy is to do genetic testing.
Results Reported As
Test Result |
Interpretation of test result |
CLEAR |
Tested mutation was not detected in animal with „clear“ result. Animal tested as clear has wild-type allele in homozygous state (i.e. two pairs of healthy alleles). It will not develop disease caused by tested mutation.* It will pass only wild-type allele to its offspring. |
CARRIER |
Tested mutation was detected in animal with „carrier“ result. Animal tested as carrier has one wild-type and one mutation allele, it is in heterozygous state. It will not develop disease caused by tested mutation.* It can pass wild-type or mutation allele to its offspring. |
AFFECTED |
Tested mutation was detected in animal with „affected“ result. Animal tested as affected has two copies of mutation alleles affecting the gene. It is likely the animal will experience a genetic disorder due to this mutation.** It will pass only mutation allele to its offspring. |
*Test excludes only tested mutation but not possible unknown mutations or factors that can lead to similar condition/symptoms.
** Potential unknown mutations or multiple other factors can possibly affect the likelihood of experiencing a genetic disorder.
References:
Merveille, A., (2011.): CCDC39 is required for assembly of inner dynein arms and the dynein regulatory complex and for normal ciliary motility in humans and dogs.
Edwards, DF., (1992.): Primary ciliary dyskinesia in the dog. Probl Vet Med. 4 (2): 291-319.
Merveille, AC., (2014.): Clinical findings and prevalence of the mutation associated with primary ciliary dyskinesia in Old English Sheepdogs. J Vet Intern Med. 28 (3): 771-8.