Skin bleeding spots

Skin diseases usually cause subcutaneous bleeding, but we also need to distinguish what kind of subcutaneous bleeding it is, because purpura subcutaneous bleeding will cause purple spots, while other skin diseases subcutaneous bleeding will cause red blood spots. When we feel itchy skin, it is easy to cause subcutaneous bleeding after scratching it hard. So what is the matter with skin bleeding spots?

Cutaneous petechiae refers to extensive or localized bleeding under the skin or mucous membranes, forming red or dark red spots on the skin or mucous membranes, with a diameter of about 3 to 5 mm or larger. Those that fade when pressed are called purpura. Usually, those with a diameter of less than 2 mm are called petechiae.

Causes and common diseases

1. Causes

(1) Extravascular factors: If the tissues surrounding blood vessels become weak due to degeneration, atrophy and relaxation, bleeding may easily occur and purpura may form. Extravascular factors are more common in senile or cachectic purpura. Capillaries and small blood vessels can be ruptured and bleed by slight external force, leading to purpura.

(2) Vascular factors: refers to purpura caused by damage to the capillary walls, which causes blood to seep out of the blood vessels. Purpura caused by vascular factors accounts for the first place among all purpura. When small blood vessels in a normal person are injured, the blood vessels immediately undergo reflex contraction and local blood flow slows down to promote hemostasis. If the peripheral blood vessels are fragile, permeable and vasomotor function is abnormal, hemorrhagic purpura may easily occur due to blood infiltration into and out of the blood vessels. The characteristic of bleeding caused by vascular factors is that the capillary fragility test is positive, but the bleeding time and clotting time are normal. The most common type of purpura is allergic purpura. Secondly, bacterial or viral infection, vitamin C deficiency, chemical factors, etc. can damage the blood vessel walls and cause purpura. In addition, there is a type of increased fragility of the blood vessel walls for unknown reasons, which is common in women. Purpura may disappear on its own without any adverse consequences. This is called simple purpura.

(3) Platelet factors: Platelets play an important role in the hemostasis process. Thrombocytopenia or platelet function deficiency will weaken or lose the hemostatic function, which can easily lead to purpura. Thrombocytopenia can be seen in idiopathic thrombocytopenia, secondary thrombocytopenia (also known as symptomatic purpura, which can be caused by bone marrow hematopoietic disorders leading to a decrease in platelets, seen in aplastic anemia, leukemia, and bone metastasis of cancer), radioactive substances and chemicals destroying megakaryocytes and reducing platelet production, severe infections (such as typhoid fever, meningitis, sepsis) causing excessive platelet destruction, etc. In addition, hypersplenism, lupus erythematosus, uremia, etc. can also cause thrombocytopenia. Platelet function deficiency diseases include hemorrhagic thrombocythemia, thrombasthenia, etc. Laboratory tests are of great significance for the diagnosis of purpura caused by platelet factors, which generally manifests as prolonged bleeding time, poor clot retraction and thrombocytopenia.

(4) Coagulation factor factors: Coagulation factor deficiency often leads to coagulation disorders and causes purpura. This type of disease is rare, and the causes are mostly congenital, with a few being acquired (mainly caused by liver disease). Purpura patients should undergo relevant examinations such as routine blood tests, platelet count, bleeding time, coagulation time, capillary fragility test, skin and mucous membrane microcirculation, blood rheology and coagulation factors.