Cyanosis is a benign functional vascular disease that is not of serious consequence, although sometimes there can be considerable discomfort and lesions, especially in combination with swelling and stiffness of the fingers. The condition generally decreases slowly in adulthood, but can also have persistent skin color changes throughout life. The prognosis for the limb and life is good without nutritional disorders, ulcers or gangrene. Understanding the extent, degree, and timing of cyanosis can help determine which diseases are causing it. 1. Generalized cyanosis with dyspnea and heartbeat is caused by respiratory disease, heart failure or congenital cardiovascular disease; without dyspnea, it may be due to methemoglobinopathy or true erythrocytosis. Cyanosis at the end of the body, accompanied by cold extremities and decreased blood pressure is caused by shock; those with a history of paroxysmal appearance of cyanosis at the extremities are paroxysmal arterial spasm disease. 2, cyanosis is extremely obvious are congenital cardiovascular disease and chronic pulmonary heart disease. Patients often have fingers and toes in the shape of drumstick, red blood cell count significantly increased; degenerative hemoglobinopathy sometimes cyanosis is also very obvious, but no fingers in the shape of drumstick performance. True erythrocytosis is usually less cyanotic. The cyanosis caused by respiratory disease is generally moderate, and the fingers may show a mild drumstick shape with a moderate increase in red blood cell count. 3. Most of those who have cyanosis since childhood are congenital cardiovascular disease. If cyanosis occurs only after contact with aniline or nitrobenzene, it may be the poisoning of these drugs.