Thrombocytopenic purpura

Introduction Thrombocytopenic purpura is characterized by scattered spots on the limbs or spread to the whole body. Severe patients with joint pain or abdominal pain, blood in the stool, vomiting blood, and collapse, etc., can develop into purpuric nephritis. Thrombocytopenic purpura is divided into primary and secondary types. Primary thrombocytopenic purpura is an immune syndrome that is a common hemorrhagic disease. It is characterized by the presence of anti-platelet antibodies in the blood circulation, causing excessive destruction of platelets and causing purpura; while megakaryocytes in the bone marrow are normal or increased, and are immature. According to the age of onset, clinical manifestations, platelet count, length of disease and prognosis, the disease was divided into acute and chronic, and the pathogenesis and performance of the two were significantly different.

Cause

The cause of thrombocytopenic purpura

The etiology and pathogenesis of this disease have not been fully elucidated. Acute type occurs mostly after acute viral upper respiratory infection has healed, suggesting that thrombocytopenia is associated with an immune response to the primary infection. About half of chronic patients can detect anti-platelet antibodies in serum.

I. Platelet-related antibodies Anti-platelet antibodies are present in the serum of chronic ITP patients. If the plasma of a chronic ITP patient is delivered to a normal person, the normal person's thrombocytopenia can be reduced. If a normal human platelet is delivered to an ITP patient, the input platelet is destroyed in a short time. It was confirmed that the shortening of platelet life in ITP patients was due to the presence of platelet-destroying antibodies in serum, called platelet-associated antibodies (PAIC3), 95% of which were IgG type, and a small amount of IgM and IgM type. Platelet-associated complement C3 (PAC3) is present in the blood circulation of ITP patients, and its increase is directly proportional to the increase in PAIg.

Second, the platelet destruction mechanism The average life expectancy of platelets is 7 to 11 days, while the lifespan of platelets in ITP patients is only 40 to 230 minutes. Because the spleen contains a large number of macrophages, it can produce high concentrations of anti-platelet antibodies, and the slow blood flow can block the antibody-coated platelets, so the spleen becomes the main site of platelet destruction. The liver and bone marrow are also places where platelets are destroyed. Chronic ITP platelet destruction is caused by the phagocytosis of macrophage cells by binding of anti-platelet antibodies to their associated antigens. Acute ITP platelet destruction is caused by the adsorption of viral antigens on the surface of platelets and binding to the corresponding antiviral antibodies, resulting in destruction of platelets.

Third, megakaryocyte maturation disorder Because platelets and megakaryocytes have a common antigen, anti-platelet antibodies can also inhibit bone marrow megakaryocytes, causing maturity disorders, thereby affecting platelet production.

Fourth, other factors 1, the role of estrogen: chronic type is more common in women of childbearing age, easy to relapse during pregnancy, suggesting that estrogen may play a role in the pathogenesis of this disease, it may be that estrogen can increase macrophage phagocytosis and destruction of platelets ability. 2, the antibody damages the capillary endothelial cells, causing the capillary permeability to increase and aggravate the bleeding.

an examination

Related inspection

Capillary fragility test bleeding time blood routine

(1) Blood image

1. Acute platelets are significantly reduced, mostly below 20 × 109 / L. When the bleeding is severe, it can be accompanied by anemia, and white blood cells can be increased. Occasionally, eosinophilia.

2. Chronic, platelets are mostly in the range of 30 ~ 80 × 109 / L, common large deformed platelets.

3. The average platelet volume (MPV) increases.

4. Platelet distribution width (PDW) changes significantly.

5. Platelet morphology is abnormal, showing large platelets, reduced particles and excessive staining.

(2) Bone marrow

Acute type, the number of megakaryocytes is normal or increased, mostly naive, with smooth cell edges, no protrusions, few cytoplasm and large particles. Chronic, megakaryocytes generally increase, granular megakaryocytes increase, but the cytoplasm contains less particles, basophilic.

(3) Immunological examination

Immune function related tests.

(4) Others

The bleeding time was prolonged, the beam arm test was positive, the blood clot contraction was poor, platelet adhesion and aggregation function were weakened, and the life of the 51Cr or 111In labeled platelets was shortened.

Differential diagnosis

The difference between thrombocytopenic purpura and leukemia

The number of normal platelets in the blood is 300,000/cm 3 , which can be reduced to 40,000 to 50,000 when the disease is sick. When the number of platelets drops to 20,000, the patient may have gastrointestinal bleeding, intracranial hemorrhage, hematuria, etc., which is life-threatening. .

The typical symptoms of thrombocytopenia are hemorrhage. In the early stage of the disease, the skin will have needle-like red spots, which will develop into massive thrombocytopenic purpura. The size of the purpura varies from small to soy, and large can reach the palm. So big. The site of thrombocytopenic purpura is generally in the parts of the skin where the skin is relatively loose, such as the neck, around the eyes, lower limbs, etc., accompanied by swelling and pain, and severe purple spots appear in the oral mucosa.

Thrombocytopenic purpura is similar to some of the symptoms of leukemia. Some patients believe that thrombocytopenic purpura is a quasi-leukemia, and the psychological stress is very high. Experts explained that it is currently believed that purpura is caused by abnormal thrombocytopenia due to simple thrombocytopenia, and thrombocytopenia and coagulation abnormality are only one of the symptoms of leukemia. Leukocytes and red blood cells in leukemia patients are not normal. They are completely different.

Diagnostic criteria

1, multiple tests to check the reduction of platelet count.

2. The number of megakaryocytes in the bone marrow examination is increased or normal, and there are mature obstacles.

3. The spleen does not increase or only slightly increases.

4, the following five points should have any point

(1) Prednisone treatment is effective.

(2) effective spleen treatment

(3) Increase in PalgG.

(4) Increased PAC. Platelet life is shortened. Exclude secondary thrombocytopenia.

Acute ITP platelets are significantly reduced, usually less than 20 x 10^9/L. Chronic ITP multiple tests for thrombocytopenia, mostly (30 ~ 80) × 10 ^ 9 / L.

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