Plus-Hex CLINICAL
Introduction
Immune-mediated thrombocytopenia( IMTP) is a condition in which the body ' s immune system incorrectly targets and destroys its own platelets. IMTP can be classified as primary or secondary; it may occur as a primary autoimmune disease( idiopathic) or secondary to an underlying disease such as infection or neoplasia [ 1 ].
Platelets( thrombocytes) are tiny cellular fragments found throughout the blood and spleen. They play a crucial role in the initial stages of blood clotting( haemostasis). Thrombopoiesis, the production of platelets from megakaryocytes, occurs continually in the bone marrow; the platelets are released into the bloodstream in response to the release of the hormone thrombopoietin to aid haemostasis [ 2 ].
There are two types of haemostasis: primary and secondary. Primary haemostasis is the initial stage of haemostasis; this involves the formation of a primary platelet plug at the site of an injury. Secondary haemostasis involves the formation of an insoluble fibrin clot by aggregated platelets and fibrin [ 1 ]. Haemostasis leads to the cessation of bleeding from the damaged blood vessels. Once haemostasis is achieved, healing of the tissues can begin [ 3 ].
Platelets are vital for forming clots as part of haemostasis. The normal circulating platelet count for a dog may be in the range of 200,000 – 500,000 /µ l, also expressed as 200 – 500 × 10 9 / l [ 4 ]. Platelets typically circulate for 8 – 12 days after they are produced and released into the bloodstream.
In the healthy patient, the liver removes expired platelets through phagocytosis [ 5 ], which in turn generates a message to the bone marrow megakaryocytes to produce more platelets. In patients with IMTP, the spleen removes the platelets via phagocytosis approximately 10 times faster than the normal rate [ 5 ], depleting the platelet store and thereby decreasing the blood ' s clotting ability.
The pathogenesis of IMTP involves the formation of antiplatelet autoantibodies, which can lead to platelet clearance and complement-mediated destruction [ 6 ]. Complement-mediated destruction occurs when components of the immune system are activated and damage platelets or mark them for faster removal from the circulation.
Cytotoxic T cells also contribute to platelet destruction and thrombocytopenia, and this may occur even when platelet-surface-associated immunoglobulins are not detectable. In addition, platelet production may be reduced by antibodies and T cells targeting megakaryocytes, as well as by inappropriately low thrombopoietin concentrations [ 6 ].
Thrombocytopenia therefore occurs when platelets are destroyed or used faster than the bone marrow can produce them. Patients with a platelet count of less than 50,000 /µ l( 50 × 10 9 / l) are considered severely thrombocytopenic [ 4 ] and are at risk of life-threatening bleeding.
Despite the fact that red blood cells( RBCs) are not being destroyed, blood loss from coagulopathy can lead to severe anaemia.
Learning outcomes
• Review the pathophysiology of IMTP
• Understand the various treatments for IMTP in canine patients
• Discuss the nursing considerations and interventions for the IMTP patient
Signalment
Species Breed Age
Dog Cockapoo 2 years Sex Female( neutered) Weight
Presentation
10.8 kg
The patient, named Peach, presented to her primary care practice in May 2024 with lethargy, hyporexia, melaena and bleeding from the mouth. Haematology on a blood sample revealed a low RBC count, and examination of a blood smear revealed a low platelet count alongside reticulocytes and polychromasia, allowing the presumptive diagnosis of IMTP.
Peach initially responded well while receiving prednisolone 10 mg( Millpledge Veterinary, 5 mg tablets) orally once daily, but suffered a relapse in September 2024, which led to the decision to refer her for specialised medical treatment.
Peach was urgently referred after developing a drop in haematocrit to 12 % and platelet count to 0 per highpower field. On presentation, Peach was quiet, alert and responsive. Her heart rate was 120 beats per minute( bpm) with synchronous but hyperdynamic pulses, and no heart murmur was auscultated.
Peach ' s mucous membranes were pale pink with some petechial haemorrhage; she was normothermic at 38.2 ° C. Peach was also passing melaena, indicative of an upper gastrointestinal tract bleed.
Volume 41( 4) • August 2026
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