IMTP in a cat

Simba, a 3 year old MN DSH was referred for further investigation of pale mucous membranes and petechiae of his gums. He was an indoor, outdoor cat who had been well until he suddenly became lethargic and anorexic two days before presenting to his referring vet. On presentation, the referring vet recognised that Simba would benefit from a blood transfusion and referred him the same day.

Simba presented late in the afternoon and was very depressed, tachycardic and tachypnoeic, with pale mucous membranes and petechiae of the gums and haemorrhage in the anterior chambers of his eyes. Bloods were taken for a complete blood count and biochemistry which confirmed severe thrombocytopenia and a regenerative anaemia. He was blood type A. FeLV and FIV were both negative. PT and APTT were within normal range.

Haematology result at admission:

Immune mediated thrombocytopenia with resulting blood loss or combined immune mediated haemolytic anaemia was considered the most likely differential as there are really no other causes of such a low platelet count. This can be primary or secondary and while it used to be considered that secondary immune mediated IMHA/IMTP was more common it is now recognised that the majority of cases are primary.

The aim was to obtain a donor to transfuse Simba the evening he was referred. However, the type A donor, a Bengal called Theo, was off on his travels and did not come home that evening so we were unable to transfuse him when we would have liked to. Simba was started on immunosuppressive doses of dexamethasone IV and monitored overnight while we hoped that Theo would come home soon.

Theo arrived the following morning, he was sedated and blood collected to give to Simba. The transfusion increased his PCV to 15% and greatly improved his demeanour and vital parameters. Abdominal ultrasound and thoracic radiographs were obtained to look for a trigger. No abnormalities were found giving a diagnosis of primary IMTP. Testing for mycoplasma was negative. Coombs and slide agglutination were both negative making it most likely that the anaemia was secondary to blood loss rather than combined IMHA/IMTP or Evan’s syndrome.

Simba was continued on immunosuppressive treatment with oral prednisolone and continued to improve. The platelet count returned to normal by the third day of treatment. Simba returned to the care of his referring vet for ongoing monitoring with the aim of slowly reducing the prednisolone. Happily, he made a full recovery.

Simba’s case is a fairly common presentation for us at SCVS and it highlights the difficulty that the lack of banked cat blood brings. Most practices rely on staff pets to act as blood donors. This limits the ability to quickly treat feline patients requiring blood as it relies on the donor cat being at home and able to come into the surgery. Donors invariable need to be sedated to take blood for donation which can be a limiting factor if the donor has eaten recently.

There is a blood bank in Portugal that can supply feline whole blood to practices in the UK. If ordered during the day Monday to Thursday it can be delivered the following day. The service is not available at weekends. Anyone interested can find out more at www.bsaanimal.co.uk. There is currently a group writing to the RCVS to ask them to reconsider their decision to not allow cat blood banking in the UK which would make treating transfusion dependent cats a far timelier and more straight forward process.