TNS (Trapped Neutrophil Syndrome) :

Trapped Neutrophil Syndrome (TNS), also known as Hereditary Neutropenia, is an inherited disease which causes a low number of neutrophils to circulate in the blood. As neutrophils are necessary for destroying bacteria, a low number of them causes affected dogs to eventually die from infections they cannot stop.

Puppies as young as 2 weeks can display signs, and usually die (or are PTS) by 4 months. Until the DNA test came out in 2007, it was very difficult to diagnose TNS because deceased puppies were often not even suspected of being affected with TNS. This, compounded with the fact that the neutrophil count may not have been much lower than expected for an affected puppy, may mean that TNS is more widely spread than initially expected.
Some of the possible signs of TNS affected puppies:

* The puppies growth rate may dramatically slow down from 2 weeks of age.
* They experience bouts of diarrhoea and fever.
* Lameness and sensitivity to pressure on joints may also occur.
* The puppies may also have an unusual head shape.

More information you can find on this website :
TNSdatabase