Immune-mediated Thrombocytopaenia

What is it?

Immune-mediated thrombocytopaenia (IMTP) is a condition characterised by the destruction of platelets by the immune system (‘immune-mediated’), resulting in abnormally low platelet numbers circulating within the blood (‘thrombocytopaenia’). This immune attack is due to antibody production against the body’s own platelets. Platelets are an important component of blood and their major function is to stop bleeding by forming blood clots within damaged vessels. Therefore, low numbers of platelets can cause complications such as bleeding, bruising and anaemia. IMTP can occur in both cats and dogs, however is seen more frequently in dogs, especially cocker spaniels, old English sheepdogs, German shepherds and poodles.

 

What are some of the symptoms?

  • Lethargy
  • Weakness
  • Increased respiratory rate
  • Bruising
  • Spontaneous bleeding
  • Pale gums
  • Dark, tarry stools
  • Blood in urine or stools
  • Small haemorrhages within the skin, gums or whites of the eyes

 

What are the causes?

IMTP’s can be either primary or secondary in origin and it is important to distinguish between the two. Primary IMTP’s occur when the body produces antibodies against its own platelets, causing the immune system to identify and destroy them. These are termed ‘idiopathic’, meaning their origin is unknown. Secondary IMTP’s occur secondary to an underlying condition, such as infection, cancer, drug therapy or vaccination reactions. In these cases, it is important to determine the underlying cause.

 

How is it diagnosed?

Clinical signs, patient history as well as full bloodwork (including a complete blood count, a clotting profile and analysis of a blood smear) are important for diagnosis of IMTP. In some cases, imaging such as x-rays and ultrasound may be required to either identify an underlying cause or detect any bleeding. A diagnosis of primary IMTP is achieved by ruling out any underlying conditions or syndromes that may result in reduced platelet numbers.

 

What treatment is involved?

Initial hospitalisation is usually required in patients diagnosed with IMTP in order to stabilise them and begin treatment. Fluid and oxygen therapy may be required for some patients, and in cases of severe anaemia, a blood transfusion may be helpful. A course of immunosuppressive drugs, such as steroids, are administered to counteract the immune response to antibodies attached to platelets. In secondary IMTP, if possible, the underlying syndrome is addressed in order to prevent further platelet destruction.

 

What about long term?

Patients with primary IMTP often require long-term management of the disease. In some cases, a long course of immunosuppressive medications at a tapering dose is required, lasting from weeks to months. However, many patients reach adequate platelet numbers after only 1 week of treatment. Those patients that respond well to therapy can go on to live a normal life. Regular check-ups and repeat blood tests are important and should be carried out 1, 3 and 6 months post treatment and then every 6-12 months for life. Owners should monitor their pets regularly for any of the above symptoms and notify their veterinarian if any are detected.

 

By Lauren Golding (DVM 3 Student) 2018

Lauren was one of our veterinary students who completed placement at East Port Veterinary Hospital.