Pelger-Huet Anomaly, an inherited condition, is a mutation of the neutrophils and eosinophils white blood cells which are actively involved in the immune system process.  This anomaly causes the nuclei within leukocyte cells to be abnormally shaped, which when circulating through the blood lead to an immune deficiency and predisposition to inflammation and bacterial infection.

These blood cell mutations are rare, but have been reported in several breeds. Puppies that survive birth usually display developmental delays and seizures and do not survive long, although many puppies die in utero when the disease is present in a homozygous form. If the disease is present in heterozygous form, the dogs are usually unaffected but will often pass along the more deadly form of the blood cell mutations to the offspring. Parents and siblings of dogs with Pelger-Huet may carry the anomaly as well without showing obvious physical signs. Occassionally the blood cell mutation can be found in connection with chondrodysplasia, another genetic disease, which causes the cartilage between the joints to deform leading to the affected animal being crippled.

Diagnosis of the blood cell mutation is usually done through tests of the bone marrow and blood to identify affected cells. Dogs with this anomaly are more susceptible to leukaemia or a pre-leukaemia condition and under microscopic examination these cells appear to be structurally very similar to leukaemia cells. Dogs that have been treated with sulfa drugs are more likely to have this mutation.

There is no recommended treatment for Pelger-Huet as it is not proven as a direct cause of any known disease, but dogs with this anomaly should are not recommended for breeding.