The rash is petechial

Introduction Skin appears as a defect: a rash is a skin lesion. There are a variety of manifestations ranging from simple skin color changes to skin surface bulging or blisters. Extensive or localized skin, submucosal hemorrhage, forming red or dark red spots on the skin and mucous membranes, about 3-5 mm in diameter or larger. Usually the diameter is less than 2 mm.

Cause

1. Extravascular factors: If the perivascular tissue is weak due to degeneration, atrophy and relaxation, it is prone to bleeding and form purpura. Extravascular factors are more common in senile or cachexia purpura. Capillaries and small blood vessels are slightly affected by a slight external force, which can cause rupture and hemorrhage.

2. Vascular factors: refers to the purpura formed by the leakage of blood from the blood vessels to the outside of the blood vessels due to damage of the capillary wall. Purpura caused by vascular factors accounted for the first place in all purpura. After a small blood vessel injury in a normal person, the blood vessel immediately undergoes a reflex contraction, and the local blood flow is slowed down to promote hemostasis. If the peripheral blood vessels are brittle, the permeability is increased, and the vasomotor function is abnormal, it is easy to cause hemorrhagic purpura due to extravasation of blood from the blood vessels. The hemorrhage caused by vascular factors is characterized by capillary fragility test, but the bleeding time and clotting time are normal. The most common form of such purpura is allergic purpura. Second, bacterial or viral infections, vitamin C deficiency, chemical factors, etc. can cause damage to the blood vessel wall and cause purpura. In addition, there is an unclear increase in the brittleness of the blood vessel wall, which is common in women. The purpura can disappear on its own and has no adverse consequences. It is called simple purpura.

3. Platelet factor; platelets play an important role in the process of hemostasis. Thrombocytopenia or defects in platelet function may result in decreased or lost hemostasis, and are prone to purpura. Thrombocytopenia can be seen in idiopathic thrombocytopenia, secondary thrombocytopenia (also known as symptomatic purpura, thrombocytopenia due to bone marrow hematopoietic disorders, seen in aplastic anemia, leukemia, cancerous bone metastasis), radiation Substances and chemicals destroy megakaryocytes, which reduce platelet production and severe infections (such as typhoid fever, meningitis, sepsis) and excessive platelet destruction.

In addition, hypersplenism, lupus erythematosus, uremia, etc. can also reduce thrombocytopenia. Platelet function-deficient diseases include hemorrhagic thrombocytosis and thrombocytopenia. Laboratory tests are important for the diagnosis of purpura caused by platelet factors, generally characterized by prolonged bleeding time, poor clot retraction and thrombocytopenia.

4. Coagulation factor: Coagulation factor deficiency often causes coagulopathy and causes purpura. These diseases are rare, the causes are mostly congenital, and a few are acquired (mainly caused by liver disease). Patients with purpura should be examined for blood routine, platelet count, bleeding time, clotting time, capillary fragility test, skin and mucous membrane microcirculation, hemorheology and coagulation factors.

an examination

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Differential diagnosis

Extensive or localized skin and submucosal hemorrhage, forming red or dark red spots on the skin and mucous membranes, about 3-5 mm in diameter or larger. Those larger than 5 mm are called ecchymoses, and local bulges or fluctuations are hematoma.

1 vascular purpura: very common, due to damage to the blood vessel wall or its fragility and permeability, common in immune (such as allergic purpura), infectious (such as sepsis), abnormal vascular structure (such as heredity) Hemorrhagic telangiectasia and other diseases such as abnormal proteinemia, simple or senile purpura. Check that there is no abnormality other than the beam arm test may be positive.

2 platelet abnormal purpura: the most common, mostly due to thrombocytopenia, increased and dysfunction, if the buccal mucosa of the buccal mucosa or blood blisters, often suggesting severe bleeding, should be actively treated.

3 coagulation mechanism disorders: including clotting factor deficiency, circulating anticoagulant substances or fibrinolytic hyperactivity, generally caused by blood clotting mechanism disorders caused by joint blood, muscle hematoma and visceral hemorrhage, less skin purpura It only shows large ecchymoses, and it has obvious abnormalities in the examination of coagulation, which can be differentiated from purpura caused by vascular purpura and platelet abnormalities. The treatment of purpura varies according to the cause.

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