Pelger-Huët Anomaly in Cats

Pelger-Huët Anomaly is a rare genetic disorder that affects white blood cells in your cat’s body. This defect causes the cells to have an unusual shape and structure as compared to normal, healthy cells. The method of inheritance is thought to be dominant and not sex-linked. This means that cats possessing only one copy of the gene for Pelger-Huët Anomaly will have the disease. In cats, so far only domestic shorthairs have been found with this condition.

Many cats suffering from Pelger-Huët Anomaly will be asymptomatic. This means that your cat may never show symptoms that they have this condition. Rarely, symptoms will occur. These typically include:

• Skeletal deformities at birth
• Stillborn kittens
• Reduced immune response

Pelger-Huët Anomaly is caused by the transferring of a defective gene from the parent to the offspring kitten. In cats affected with this condition, the genetic defect causes white blood cells to be bilobed or dumbbell shaped. The total white blood cell count will be normal, with only the appearance of the cells’ shape being different.

Heterozygous 

When your cat inherits only one copy of the defective gene from one of its parents, this is referred to as heterozygous Pelger-Huët Anomaly. In the heterozygous form, most cats will not show any symptoms of the disease.

Homozygous 

Homozygous Pelger-Huët Anomaly occurs when your cat inherits two copies of the affected gene. In order for this to happen, both the mother and father would have had to possess a copy to pass on to their offspring. When symptoms do occur, it is typically in instances of homozygous Pelger-Huët Anomaly.

Since most affected cats will not show any signs of the condition, Pelger-Huët Anomaly is typically diagnosed as part of the investigation of another condition. In rare cases which a reduced immune response is observed, diagnosis will be part of a normal evaluation of the white blood cell makeup of your cat’s blood. Diagnosis also may be made as part of an investigation into increased rate of birth mortality either in a single litter or in multiple litters by cats used in breeding programs.

The definitive diagnosis of the disease will require your veterinarian to collect a blood sample. This will involve a quick and painless procedure in which your vet inserts a needle into your cat’s vein and withdraws a small sample of blood. Either your vet or their laboratory will then examine the blood under a microscope. The misshapen qualities of the white blood cells will typically be readily recognizable. If this condition is suspected, you should attempt to provide your vet with a blood sample from your cat’s mother and father. This will aid in providing a definitive diagnosis and also help determine which parent possesses the defective gene.

In some cases of Pseudo Pelger-Huët Anomaly, the shape of the white blood cells in your cat may temporarily change shape. This is often caused by an underlying bacterial infection or some cases of FeLV, or feline leukemia virus. Your vet will be able to distinguish these conditions via the presence of other symptoms not typically found in Pelger-Huët Anomaly and through the use of additional diagnostic blood tests.

There is currently no treatment for Pelger-Huët Anomaly in cats. In cases which your cat suffers from poor immune response, your vet may recommend limiting contact with other cats or exposure to the outdoors. In immune-compromised cats, you should also maintain a strict preventative care schedule including maintenance of teeth and gums, tick and flea control, and regular vet visits to reduce your cat’s risk of becoming sick.

In most cats, prognosis for long-term management of Pelger-Huët Anomaly is very good. If your cat is asymptomatic, it will have a good quality and length of life and show no indications of the disease. In cats which are being considered for use in breeding programs, you should speak to your vet regarding modes of inheritance. A veterinarian qualified in reproductive issues may be able to help you determine the correct use of the affected cat in any breeding programs. In many cases, it may be advisable to spay or neuter the affected cat, thus eliminating the possibility for transmission of the defect to future generations.