Pelger-Huët Anomaly in Dogs

Pelger-Huët anomaly was first described as an abnormality of white blood cells in 1928 by Pelger, a Dutch hematologist. In 1931, Huët, who was a pediatrician, identified that the anomaly was an inherited condition.  A dog found to have Pelger-Huët anomaly will not show signs of the disorder as it does not affect the health of canines. It is discovered when a pet has routine blood tests. The prognosis is excellent as there are no links to health issues. There is no predisposition to the sex of the canine but the Australian Shepherd has been documented as predisposed after numerous studies. Others breeds recorded as known to have had the white blood cell anomaly are the Samoyed, Basenji, Australian Cattle Dog, Border Collie, Boston Terrier, Foxhound, Coonhound, German Shepherd, Cocker Spaniel, and mixed breed.

The failure of the white blood cells to mature normally is called Pelger-Huët anomaly. This is a rare condition that does not cause clinical signs. It is of an autosomal dominant inherited pattern and is characterized on blood tests by cells that have neutrophils and eosinophils that have abnormal nuclei based on their immaturity.

The Pelger-Huët anomaly does not show any clinical signs in dogs. It does not cause health issues and does not cause a dog to be prone to other underlying or concurrent disease. In fact, the incidence of this condition is rare.

Types

Heterozygous phenotype describes this variance of the anomaly as one that does not affect the health of canines and has neutrophils and eosinophils present in the blood which have normal function.

Homozygous phenotype is the variant whereby pups either die in utero or are stillborn. This type is very rare in canines.

It should be noted that there is also a condition called pseudo-Pelger-Huët which is an acquired condition and can occur due to factors like a long-term illness or drug therapy.

Pelger-Huët anomaly is an inherited congenital (present at birth) condition. 

• The white blood cells have not matured
• There is hyposegmentation (which means the cell has lower than normal amount of lobes within)
• Granuloctye (neutrophils, eosinophils, basophils) nuclei are abnormal but the condition is benign
• Heterozygous dogs have two different copies of a gene, one mutated
• Homozygous canines carry both copies of the mutated gene
• Heterozygous pets have no symptoms
• Pelger-Huët anomaly is fatal for homozygous dogs; if they make it to birth they have skeletal deformities and are stillborn

Because there are no symptoms or illnesses related to Pelger-Huët anomaly, it is most often diagnosed in a routine blood test or during complete blood count analysis as part of another diagnostic procedure. When questions arise because of the test, further investigation is done by taking a sample of the blood and analyzing it under the microscope. This is called a blood smear. A blood smear can identify disorders affecting the cells, like the neutrophils, eosinophils and basophils that will be mutated in the case of Pelger-Huët anomaly.

There is no treatment indicated for Pelger-Huët anomaly. Some owners may want to organize the testing via complete blood count of the parents and siblings of their family pet, to raise awareness of the potential risk of when breeding, as homozygous dogs will die in utero or be stillborn.

There is no follow up required for the abnormal formation and immaturity of the white blood cells as there are no diseases or dangers to your dog associated with this anomaly. In addition, you should not breed your dog in the likelihood that the anomaly could be passed on to the next generation.