TNS - Trapped Neutrophil Syndrome

The Disease

TNS is a hereditary disease where the bone marrow produces neutrophils (white cells) but is unable to effectively release them into the bloodstream. Affected puppies have an impaired immune system and will eventually die from infections they cannot fight. Once thought to be rare, it is now believed that the disease goes undiagnosed for several reasons. Even when looking, blood counts do not always show lower than normal neutrophil (white blood cell) counts. Because it is an autoimmune-deficiency disease, young puppies present a variety of symptoms depending upon what infections they fall prone to. Thus many cases are not properly diagnosed and have just been thought to be "fading puppies".The age of onset varies depending on which infection is involved at the time. Most puppies become ill before leaving the breeder but some do not have symptoms until later. Most affected puppies die or are euthanised by about 4 months of age.


Trait of Inheritance

TNS follows an autosomal recessive mode of inheritance.




Genotype: N / N [ Homozygous normal ]

The dog is noncarrier of the mutant gene.

It is very unlikely that the dog will develop Trapped Neutrophil Syndrome ( TNS ). The dog will never pass the mutation to its offspring, and therefore it can be bred to any other dog.



Genotype: N / TNS [ Heterozygous ]

The dog carries one copy of the mutant gene and one copy of the normal gene.

It is very unlikely that the dog will develop Trapped Neutrophil Syndrome ( TNS ) but since it carries the mutant gene, it can pass it on to its offspring with the probability of 50%.

Carriers should only be bred to clear dogs.

Avoid breeding carrier to carrier because 25% of their offspring is expected to be affected (see table above).



Genotype: TNS / TNS [ Homozygous mutant ]


The dog carries two copies of the mutant gene and therefore it will pass the mutant gene to its entire offspring.

The dog is likely to develop Trapped Neutrophil Syndrome (TNS) and will pass the mutant gene to its entire offspring.



The genetic defect leading to the disease has been identified. By DNA testing, the responsible mutation can be shown directly. This method provides a very high accuracy test and can be done at any age. It offers the possibility to distinguish not only between affected and clear dogs, but also to identify clinically healthy carriers. This is an essential information for controlling the disease in the breed, as carriers are able to spread the disease in the population, but can not be identified by means of common laboratory diagnostic.


Trapped Neutrophil Syndrome (TNS), Laboklin, accessed 11 January 2019, <>


Laboklin and Animal DNA Diagnostics offers members of the Society a process for submitting DNA tests, and DNA is extracted from a sample. See their individual websites for further information of how to order a test. 


Laboklin -

Animal DNA Diagnostics -