Trapped Neutrophil Syndrome (TNS) is a mutation causing the dog's infection-fighting white blood cells to not be released from the bone marrow. The dog's immune system is unable to fight off infections and the dog eventually dies, usually when they are a few months old. Age of onset from birth, but symptoms may not be apparent until 7 months. An affected puppy may not show any specific symptoms, other than susceptibility to infection, but may be smaller and less healthy than unaffected puppies.