Trapped Neutrophil Syndrome

Trapped Neutrophil Syndrome (TNS), also called hereditary neutropenia, is a rare blood disease of the Border Collie affecting puppies between 2 weeks and 7 months of age. The disease is characterised by deficiency of segmented neutrophils in the blood and hyperplasia of myeloid cells in the bone marrow. As a result, the immune system becomes compromised and fails to protect against infections. The widespread nature of the disease indicates that the mutation of the gene responsible for this condition was either already present in the founder dogs used to establish the breed, or originated very early in the breed. The carrier frequency of this fatal, inherited canine disease is rather high (11.1%).4 TNS has also been associated with previous drug therapy, particularly with anti-seizure medications, and sulfa drugs.3,1

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Severely affected puppies have narrowed elongated skull shape described by breeders as ferret-like. Puppies are often smaller than their litter mates and suffer from chronic infections and failure to thrive. Clinical signs may include fever, lameness, swelling of the joints, loss of appetite, and diarrhea. There is usually a good response to long-term corticosteroid treatment; however, care is required to avoid their adverse effects. It is also imperative that medications are not withdrawn abruptly, as a second remission may not always be achievable.


  1. Mordecai Siegal. UC Davis Book of Dogs: The Complete Medical Reference Guide for Dogs and Puppies
  2. Perkins MC, Canfield P, Churcher RK, Malik R. Immune-mediated neutropenia suspected in five dogs. In: Aust Vet J. 2004 Jan-Feb;82(1-2):52-7.
  3. Jeremy R Shearman1, and Alan N Wilton. A canine model of Cohen syndrome: Trapped Neutrophil Syndrome
  4. Real-Time PCR Genotyping Assay for GM2 Gangliosidosis Variant 0 in Toy Poodles and the Mutant Allele Frequency in Japan

Bacteria that are in the process of being phagocytized by a blue-colored neutrophil.
Credit: CDC/National Institute of Allergy and Infectious Diseases (NIAID)

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