What Is Immune-Mediated Thrombocytopenia?

Primary immune thrombocytopenia (ITP), previously called idiopathic thrombocytopenic purpura, is an acquired autoimmune disease. It is the most common hemorrhagic disease caused by a decrease in platelet count seen clinically. Through the study of platelet-related antibodies in patients, it is currently recognized that most ITPs are caused by the excessive destruction of immune-mediated autoantibodies-induced platelets by the monocyte macrophage system. There is also a new view that immune-mediated damage to megakaryocytes or inhibition of megakaryocyte release of platelets, resulting in insufficient platelet production in patients. Clinical manifestations of platelet count decreased to varying degrees, with or without skin and mucous membrane bleeding symptoms. ITP can occur at all ages. Generally, children are of the acute type and adults are of the chronic type. The two types differ in age, etiology, pathogenesis, and prognosis.

Basic Information

nickname: Idiopathic thrombocytopenic purpura
English name: primary immunologic thrombocytopenic purpura
Visiting department: Internal medicine
Common locations: Skin, mucous membrane

Common causes: Antiplatelet autoantibodies, abnormal T cells, immune response to platelet-associated antigens, and viral infections
Common symptoms: The most common are distal skin ecchymosis, oral mucosa, blood bubbles on the tongue, bleeding gums and nasal cavity, increased menstrual flow, fatigue, etc.

Causes of primary immune thrombocytopenia

Antiplatelet autoantibodies

Most patients have a negative correlation between antiplatelet autoantibodies and platelet counts. The site where antiplatelet autoantibodies are known is mainly in the spleen. At the same time, the main organ for platelet destruction is also the spleen, indicating that the spleen plays a central role in the pathogenesis of ITP.

2. T cell abnormalities

Platelet-reactive T cells have been found in the blood of ITP patients.

3. Platelet-associated antigen

Some scholars believe that the body's immune response to platelet-associated antigens causes thrombocytopenia.

4. Viral infection

Acute ITP in children is often associated with viral infections. It is an immune complex disease caused by a natural immune defense response after viral infections.

Clinical manifestations of primary immune thrombocytopenia

Clinically, it can be divided into acute type and chronic type according to the course of ITP patients. Those with a disease duration of less than 6 months are referred to as acute, and those with a disease duration greater than 6 months are referred to as chronic. Some are acute to chronic.

Acute ITP

Generally onset is rapid, showing systemic bleeding in multiple parts of the skin and mucous membranes. It is most common in skin ecchymosis of the distal part of the limb. In severe cases, ecchymosis can be fused into a slice or form a blood bubble. Bleeding from oral mucosa, tongue, bleeding gums and nasal cavity. A few may have bleeding in the digestive tract and retina. Intracranial hemorrhage is rare, but it can still occur when acute platelet reduction is significant and life-threatening. Acute ITP is mostly self-limiting, and part of the course of disease is not cured, and it is converted to chronic ITP.

2. Chronic ITP

Generally onset, the symptoms of bleeding are related to platelet counts, and 30% to 40% of patients have no symptoms at diagnosis. It mainly manifests small skin bleeding points or ecchymoses of different degrees, especially after scratching or trauma. Women can show increased menstrual flow.

3. fatigue

Many patients have obvious symptoms of fatigue, and some patients are more prominent. It is also an indication of disease treatment for those with apparent weakness.

Primary immune thrombocytopenia test

Blood routine

Platelet counts were reduced to varying degrees, and platelet size and morphology were abnormal. Generally no significant leukopenia and hemoglobin reduction.

2. Bone marrow examination

Mainly changes in megakaryocyte lines. The number of bone marrow megakaryocytes is increased or normal. But the number of megakaryocytes that can produce platelets is significantly reduced or lacking. Prominent changes are imbalance of nuclear plasma maturation of megakaryocytes, particles in the cytoplasm are reduced, and vacuoles and denaturation appear.

3. Determination of antiplatelet antibodies

Most patients with ITP have elevated levels of antiplatelet antibodies.

Diagnosis of primary immune thrombocytopenia

The diagnosis of TP is based on clinical signs of bleeding, decreased platelet counts, no enlarged spleen, qualitative and quantitative changes in bone marrow megakaryocytes, and antiplatelet antibody testing. The 5th National Conference on Thrombosis and Hemostasis proposed diagnostic criteria:

1. Repeated laboratory tests have reduced platelet counts.

2. The spleen is not enlarged or only slightly enlarged.

3. The number of megakaryocytes in bone marrow examination is increased or normal, and there are obstacles to maturity.

4. One of the following 5 items:

(1) Prednisone is effective.

(2) Spleen resection is effective.

(3) Antiplatelet antibodies increase.

(4) Platelet-related complement C3 increased.

(5) The platelet life test is shortened.

5. Exclude secondary thrombocytopenia.

Differential diagnosis of primary immune thrombocytopenia

ITP is an exclusionary diagnosis. Care must be taken to distinguish it from various secondary thrombocytopenia.

Pseudo thrombocytopenia

The common cause is that the intravascular EDTA anticoagulant caused platelets to aggregate in vitro, which caused the cell counter to misidentify during machine testing. The incidence rate is 0.09% 0.21%.

2. Various autoimmune diseases

Such as systemic lupus erythematosus, Sjögren's syndrome, etc., can reduce platelet counts before or during the diagnosis of the disease.

3. Hypersplenism

Decreased platelet count may be the primary manifestation of the disease, but splenomegaly is a unique clinical feature.

Primary immune thrombocytopenia treatment

Because children's acute ITP is often related to viral infections, and most of them are self-limiting, symptomatic treatment is the main.

Spontaneous complete and long-lasting remission of ITP in adults is <10%, and the principle of treatment should be to stop bleeding rather than promote platelets to normal. The need for treatment depends primarily on the severity of the patient's bleeding rather than focusing too much on the platelet count. Those with platelet counts exceeding 30 × 10 / L and asymptomatic generally do not require treatment.

Glucocorticoid

Is the drug of choice for the treatment of ITP. Applicable platelet count <30 × 10 / L, and severe bleeding; or risk of bleeding; or obvious symptoms of fatigue. Prednisone is generally preferred for oral administration. After the treatment is effective, the dose is gradually reduced until the drug is discontinued.

2. High-dose intravenous gamma globulin

Applied in the case of emergency bleeding, the side effects are slight.

3. splenectomy

Splenectomy is considered to be the main treatment after glucocorticoids. For glucocorticoid treatment ineffective or dose-dependent. The effective rate is 60% to 80%.

4. Other immunosuppressants

Including danazol, vincristine, cyclophosphamide, cyclosporine A, azathioprine, and the like. For patients with chronic ITP who are not well treated by glucocorticoid or splenectomy, or who are not suitable for glucocorticoid or splenectomy, they can be treated with a single drug or a combined regimen.

5. Thrombopoietin receptor agonists

It is an update of the treatment concept related to the research results of pathogenesis. Including thrombopoietin (TPO), TPO peptidomimetics and non-peptidomimetic TPO analogs. These drugs are well tolerated and have minor adverse effects.

6. Rituximab (rituximab, anti-CD20 monoclonal antibody, melanovir)

Can inhibit the production of anti-platelet autoantibodies abnormal B cells. The ITP has achieved long-term sustained relief, but its onset is slower and more expensive.

Prognosis of primary immune thrombocytopenia

1. Children's ITP

Regardless of treatment, more than 80% of patients returned to normal platelet count within 6 weeks. Only a small proportion are converted to chronic ITP.

2. Adult ITP

Few spontaneous remissions. About 1/3 of the patients were ineffective for glucocorticoids and splenectomy, and the delay was unhealed. But most have a good prognosis, and the mortality rate is not higher than the general population. About 5% of patients die from intracranial hemorrhage.