DNA test - TNS
Trapped neutrophil syndrome
Trapped Neutrophil Syndrome (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. 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. The condition is the result of a single recessive gene mutation.
Source of DNA Test: http://www.thekennelclub.org.uk/download/8288/dnatestsworldwide.pdf