# ITP in Cats: Immune-Mediated Platelet Destruction Explained Immune thrombocytopenia (ITP) in cats is a rare condition in which the immune system mistakenly destroys the cat's own platelets, the tiny cell fragments that start blood clotting [1][2]. With too few platelets, a cat can bruise easily or bleed from the nose, gums, or gut. ITP is uncommon in cats compared with dogs, but it can be serious and even life threatening [3]. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## Quick Answer - ITP means the immune system attacks and destroys platelets, so blood cannot clot normally [1][2]. - Cats with ITP often have very low platelet counts, sometimes 50,000/µL or lower, and many show obvious bleeding [2][4]. - Common first signs are small bruises on the skin and gums, nosebleeds, blood in the stool, or bleeding that will not stop after a shot or surgery [5]. - ITP is diagnosed by ruling out other causes of low platelets, and sometimes a specialized test can detect antibodies stuck to platelets [3][6]. - Treatment usually starts with steroids, and other drugs or surgery may be added for cats that do not respond [7]. ## What Is ITP in Cats? Platelets are small, cell-like fragments made in the bone marrow [1]. When a blood vessel is injured, platelets rush to the spot and clump together to form a plug that slows or stops bleeding [1][5]. They also release substances that help finish the clotting process [1]. In ITP, the immune system makes antibodies that attach to platelets. The body then removes those tagged platelets from the bloodstream, mainly in the spleen and liver [1][2]. The bone marrow may still be making platelets normally, but they are destroyed faster than they can be replaced. Veterinarians divide ITP into two types. Primary ITP means the immune attack happens on its own, with no other disease driving it [3]. Secondary ITP means something else triggered the immune response, such as an infection, cancer, drug reaction, or another immune disorder [3]. Telling these apart matters because secondary ITP may improve when the underlying trigger is treated. ITP is one of several causes of low platelets, a condition called thrombocytopenia [5]. Low platelets in cats can also come from bone marrow disease, heavy bleeding, severe clotting problems, an enlarged spleen trapping platelets, or certain drugs and toxins [1]. That is why your veterinarian will look for other explanations before settling on ITP. ## Signs Owners Notice First Platelet problems tend to cause small surface bruises and bleeding from body openings instead of large deep pools of blood [5]. Owners often spot the problem before a veterinarian does. ### Bruising and Petechiae Tiny pinpoint red or purple spots on the gums, inner eyelids, or belly are called petechiae. Larger flat bruises are called ecchymoses. These appear because small amounts of blood leak under the skin when platelets are too low to seal tiny vessel injuries [5]. ### Bleeding From the Nose, Mouth, or Gut Nosebleeds are a classic sign [5]. Some cats bleed from the gums or have blood in the stool, which may look black and tarry because digested blood turns dark [5]. Oral hematomas, which are blood-filled swellings in the mouth, have been reported as the main sign in at least one cat with primary ITP [8]. ### Bleeding After Procedures A cat with ITP may bleed longer than expected after a blood draw, vaccination, or surgery [5]. Sometimes the first clue is a bruise that keeps growing at an injection site. ### Other Signs Many cats with ITP are also anemic, meaning they have too few red blood cells, because they have been bleeding [9][4]. You might notice pale gums, weakness, or a cat that tires quickly. Some cats have no outward bleeding at all and are diagnosed only because a routine blood count showed low platelets [2]. ## Causes and Risk Factors Primary ITP is rare in cats [2][10]. When it does occur, the immune system targets platelets for no clear external reason [3]. Secondary ITP is more common and happens when another condition sets off the immune attack [3]. Possible triggers include infections, cancer, immune-mediated diseases, and reactions to certain drugs [3]. The evidence for which specific conditions act as triggers in cats is not well established, and veterinarians often cannot identify a cause even after testing [3]. Some demographic patterns have emerged. In one study of cats with suspected immune-mediated platelet destruction, younger cats were more likely to test positive for platelet-bound antibodies [6]. In a case series of 17 cats with primary ITP, the median age at diagnosis was about 4 years, with a range from 7 months to 16 years [4]. Breed and sex do not appear to be strong risk factors in cats, unlike in dogs, where middle-aged female Cocker Spaniels are overrepresented [2]. If your cat has low platelets, your veterinarian will also consider non-immune causes such as bone marrow disease, drug reactions, toxins, and platelet trapping by an enlarged spleen [1]. These are not ITP, but they can look similar on a blood count. ## How Veterinarians Diagnose ITP in Cats ITP is a diagnosis of exclusion [3]. That means your veterinarian confirms low platelets, then rules out other reasons for the low count before concluding the immune system is the culprit. ### Step 1: Confirm the Low Platelet Count A complete blood count (CBC) measures platelets. Automated machines can undercount platelets, so a veterinarian may check a blood smear by hand to confirm the number is truly low [2]. ### Step 2: Look for Bleeding and Other Clues Your veterinarian will examine your cat for bruises, petechiae, nosebleeds, and blood in the stool [5]. Blood work can show anemia from blood loss, and a clotting panel can check whether clotting proteins are working normally [5]. ### Step 3: Rule Out Other Causes Testing may include screening for infections, imaging to look at the spleen and other organs, and sometimes a bone marrow sample. Bone marrow disease, toxins, and drugs can all lower platelet production [1]. An enlarged spleen can trap platelets and lower the count in the blood [1]. ### Step 4: Look for Immune Evidence A newer test called a flow cytometry-based direct antiglobulin test can detect IgG antibodies bound to a cat's platelets [6]. In one evaluation, healthy cats had 0 to 10 percent IgG-positive platelets, and a cutoff above 10 percent was used to classify cats as positive [6]. About 23 percent of thrombocytopenic cats in that evaluation tested positive, and positive cats tended to have lower platelet counts [6]. This test is a useful adjunct, but it does not replace the full diagnostic workup [6]. For a deeper look at the diagnostic process, see [Feline Immune-Mediated Thrombocytopenia: Diagnosis and Management](/knowledge/veterinary-medicine/clinical-methods/feline-immune-mediated-thrombocytopenia-diagnosis-management) and [Thrombocytopenia in Dogs and Cats: Diagnostic Approach and Differential Prioritization](/knowledge/veterinary-medicine/clinical-pathology/thrombocytopenia-dogs-cats-diagnostic). ### Platelet Count Ranges at Diagnosis | Finding | Typical Range | Source | |---|---|---| | Normal platelet count | Roughly 200,000 to 500,000/µL | General veterinary knowledge | | Mild to moderate thrombocytopenia | 50,000 to 100,000/µL | [2] | | Severe thrombocytopenia in ITP cats | Median 10,000/µL (range 5,000 to 50,000/µL) | [4] | | Platelet count goal for medical control | Above 57,000/µL | [10] | ## Treatment Options Treatment aims to stop the immune attack, control bleeding, and support your cat while platelets recover. There are no evidence-based treatment guidelines specific to cats, so veterinarians often adapt approaches used in dogs [7]. ### First-Line Treatment Immunosuppressive doses of glucocorticoids (steroids) are the first-line treatment for ITP in dogs and cats [7]. Your veterinarian calculates the exact dose based on your cat's weight and health. Steroids work by dampening the immune response that is destroying platelets. ### Additional Immunosuppressive Drugs If steroids alone are not enough, veterinarians may add a second drug. Options include azathioprine, modified cyclosporine, and mycophenolate mofetil [7]. In one case series of 17 cats with primary ITP, all cats received corticosteroids and 14 also received cyclosporine [4]. The choice of drug is usually based on clinician preference and the individual cat's needs [7]. ### Supportive Care Cats with severe bleeding may need a transfusion of packed red blood cells or platelet-containing products [7]. Hospitalization may be needed for close monitoring. In a study of 31 cats with primary ITP, 87 percent of the cats were included in the outcome analysis, and hospitalization duration was one of the factors studied [10]. ### Treatment for Refractory Cases When ITP does not respond to standard treatment, veterinarians may consider vincristine, human intravenous immunoglobulin, splenectomy, or thrombopoietin receptor agonists [7]. These are usually reserved for refractory cases, and when to use them is still debated [7]. Romiplostim is a thrombopoietin receptor agonist that stimulates platelet production. It was used successfully in a British Shorthair cat with primary ITP that had relapsed after steroids and did not respond to chlorambucil [9]. The cat was treated with romiplostim, then splenectomy and mycophenolate mofetil, and remained in treatment for 6 months [9]. This was the first known use of romiplostim in a cat with ITP, and its effectiveness with long-term use may vary [9]. ## Recovery, Outlook, and Long-Term Management The outlook for cats with ITP varies widely. Some respond quickly to steroids, while others need months of treatment and may relapse. In a case series of 17 cats with primary ITP, 13 cats reached a platelet count above 100,000/µL at a median of 15 days after diagnosis, though the range was wide, from 2 to 207 days [4]. Only one cat achieved a full remission [4]. Relapse occurred in 10 cats (59 percent) at a median of 191 days after diagnosis, usually after medication was reduced or stopped [4]. Median survival time was about 1,067 days [4]. In a larger study of 31 cats with primary ITP, 27 of 31 cats (87 percent) were included in the outcome analysis [10]. The study looked at factors like age, sex, breed, body weight, initial platelet count, and whether blood products were given, to see how they related to outcomes [10]. Long-term management usually involves slowly tapering immunosuppressive drugs while monitoring platelet counts with regular blood tests. Your veterinarian will set the taper schedule based on your cat's response. Some cats need treatment for a year or longer [4]. If your cat has other immune-mediated conditions, such as immune-mediated hemolytic anemia or immune-mediated neutropenia, those may need separate management. You can read more about these at [Feline Immune-Mediated Hemolytic Anemia: Diagnosis and Management](/knowledge/veterinary-medicine/clinical-methods/feline-immune-mediated-hemolytic-anemia-diagnosis-management) and [Feline Immune-Mediated Neutropenia: Diagnosis and Management](/knowledge/veterinary-medicine/clinical-methods/feline-immune-mediated-neutropenia-diagnosis-management). ## Prevention Primary ITP cannot be prevented because it arises from an immune system that attacks the body's own platelets without an external trigger [3]. There is no vaccine or lifestyle change that stops it from developing. For secondary ITP, the best approach is to manage any underlying condition that could be driving the immune response [3]. Regular veterinary checkups can help catch infections, cancers, or other diseases early. If your cat takes a medication that could affect platelets, your veterinarian will monitor blood counts as needed. If your cat has been diagnosed with ITP, avoiding situations that could cause bleeding or injury makes sense. Keep your cat indoors, limit rough play, and tell any veterinarian or groomer about the diagnosis before procedures. ## Limitations and When to Contact a Veterinarian ITP is rare in cats, and much of what veterinarians know comes from dogs or from small case series [2][10][4]. Individual cats can respond very differently to treatment, and no single test confirms the diagnosis on its own [3]. Your veterinarian needs to evaluate your cat in person to make treatment decisions. Contact your veterinarian the same day if you notice new bruises, pinpoint red spots on the gums or skin, a nosebleed that stops on its own, or black tarry stool. Go to an emergency clinic immediately if bleeding will not stop, your cat is weak or collapsing, gums are very pale or white, your cat is breathing hard, or you see blood pooling in the mouth or coming from the rectum. Schedule a routine visit if your cat has been diagnosed with ITP and you notice any change in appetite, energy, or behavior, or if you are having trouble giving medications at home. ## Frequently Asked Questions ### Is ITP in cats contagious to other pets or to people? No, ITP is not contagious. It is an immune system disorder in which a cat's own body destroys its platelets [1][2]. Other cats and people in the household are not at risk of catching it. ### Can a cat with ITP live a normal life? Many cats can live for years with treatment and monitoring. In one case series, median survival time was about 1,067 days after diagnosis [4]. However, relapses are common and some cats need long-term medication [4]. ### Does a low platelet count always mean my cat has ITP? No, low platelets have many possible causes. Bone marrow disease, heavy bleeding, an enlarged spleen, drugs, and toxins can all lower platelet counts [1]. ITP is diagnosed only after other causes are ruled out [3]. ### Will my cat need a blood transfusion? Not always. Transfusions are used for cats with severe bleeding or anemia, and they are often reserved for more serious cases [7]. Your veterinarian will decide based on your cat's platelet count, red blood cell count, and clinical signs. ### Can ITP in cats be cured? Some cats achieve remission, but full remission is uncommon. In one case series, only one of 17 cats reached full remission, though most responded to treatment initially [4]. Many cats need ongoing management, and relapses can occur when medication is reduced [4]. ## Related Articles - [Feline Immune-Mediated Thrombocytopenia: Diagnosis and Management](/knowledge/veterinary-medicine/clinical-methods/feline-immune-mediated-thrombocytopenia-diagnosis-management) - [Thrombocytopenia in Dogs and Cats: Diagnostic Approach and Differential Prioritization](/knowledge/veterinary-medicine/clinical-pathology/thrombocytopenia-dogs-cats-diagnostic) - [Aortic Thromboembolism FATE in Cats: Saddle Thrombus Pain and Prognosis](/knowledge/veterinary-medicine/internal-medicine/aortic-thromboembolism-fate-in-cats-saddle-thrombus-pain-and-prognosis) - [Feline Immune-Mediated Hemolytic Anemia: Diagnosis and Management](/knowledge/veterinary-medicine/clinical-methods/feline-immune-mediated-hemolytic-anemia-diagnosis-management) - [Feline Immune-Mediated Neutropenia: Diagnosis and Management](/knowledge/veterinary-medicine/clinical-methods/feline-immune-mediated-neutropenia-diagnosis-management) - [Blood Transfusion in Dogs and Cats: Crossmatching and Compatibility](/knowledge/veterinary-medicine/emergency-critical-care/blood-transfusion-dogs-cats-crossmatching-compatibility) - [IMHA in Dogs and Cats: Immune-Mediated Anemia Explained](/knowledge/veterinary-medicine/senior-and-chronic-care/imha-dogs-cats-explained) - [IMHA Testing: Blood Smear and Bloodwork in Cats](/knowledge/veterinary-medicine/senior-and-chronic-care/imha-testing-bloodwork-cats) - [High Neutrophils in Cats: What Bloodwork Shows](/knowledge/veterinary-medicine/vet-visit-decisions/cat-bloodwork-high-neutrophils) ## References 1. [Platelets of Cats - Cat Owners](https://www.merckvetmanual.com/cat-owners/blood-disorders-of-cats/platelets-of-cats). Merck Veterinary Manual. 2. [Platelet Disorders in Animals - Circulatory System](https://www.merckvetmanual.com/circulatory-system/hemostatic-disorders/platelet-disorders-in-animals). Merck Veterinary Manual. 3. [ACVIM consensus statement on the diagnosis of immune thrombocytopenia in dogs and cats](https://pubmed.ncbi.nlm.nih.gov/38752421/). Journal of veterinary internal medicine, 2024. 4. [Primary Immune Thrombocytopenia in 17 Cats: A Case Series](https://pubmed.ncbi.nlm.nih.gov/42014091/). Journal of the American Animal Hospital Association, 2026. 5. [Bleeding and Clotting Disorders in Cats - Cat Owners](https://www.merckvetmanual.com/cat-owners/blood-disorders-of-cats/bleeding-and-clotting-disorders-in-cats). Merck Veterinary Manual. 6. [EXPRESS: Flow cytometry-based direct antiglobulin test for suspected feline immune-mediated thrombocytopenia: Assay development and demographic factors associated with DAT positivity](https://pubmed.ncbi.nlm.nih.gov/42572226/). Journal of feline medicine and surgery, 2026. 7. [ACVIM consensus statement on the treatment of immune thrombocytopenia in dogs and cats](https://pubmed.ncbi.nlm.nih.gov/38779941/). Journal of veterinary internal medicine, 2024. 8. [Oral haematomas as the major presenting sign of primary immune thrombocytopenia in a cat](https://pubmed.ncbi.nlm.nih.gov/40291440/). JFMS open reports, 2025. 9. [Use of Immunosuppression, Romiplostim, and Splenectomy to Achieve Remission in a British Shorthair Cat With Primary Immune-Mediated Thrombocytopenia](https://pubmed.ncbi.nlm.nih.gov/40525770/). Journal of veterinary internal medicine, 2025. 10. [Treatment outcomes and prognostic indicators of primary immune thrombocytopenia in 31 cats: a multicenter retrospective study (2000-2023)](https://pubmed.ncbi.nlm.nih.gov/41742513/). Journal of veterinary internal medicine, 2026. ## Further Reading - [Merck Veterinary Manual: Cat Owners](https://www.merckvetmanual.com/cat-owners) - [Cornell Feline Health Center: Health Information](https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information) - [American Veterinary Medical Association: Pet Care](https://www.avma.org/resources-tools/pet-owners/petcare)