Overview
Sickle cell anemia, also known as sickle cell anemia and sickle cell anemia, is an autosomal dominantly inherited hemoglobinopathy due to the replacement of amino acid glutamic acid at position 6 of the β-peptide chain by valine, which constitutes sickle hemoglobin and replaces normal hemoglobin. Clinical manifestations include chronic hemolytic anemia, susceptibility to infection and recurrent pain crisis causing chronic local ischemia and thus organ and tissue damage. It is mainly treated by blood transfusion and medication. The prognosis is poor for pure patients and relatively good for heterozygous patients.
Causes
This disease is an autosomal dominant hemoglobinopathy, due to the replacement of amino acid glutamic acid by valine at the 6th position of the β-chain, forming an abnormal hemoglobin S (HbS), which replaces the normal hemoglobin (HbA). When the partial pressure of oxygen decreases the molecules of hemoglobin S interact with each other, and become a helical multimer, which distorts the erythrocytes to form a sickle-shaped cell (i.e., sickle-change phenomenon). Sickled red blood cells can undergo hemolysis and block capillaries, causing related symptoms.
Symptoms
The sickling phenomenon is not obvious when the patient is born because of the high proportion of embryonic hemoglobin (HbF). Anemia symptoms such as dizziness and fatigue, as well as jaundice, appear only after 3-4 months, and liver and spleen enlargement and developmental delay can be seen after 6 months. Due to the stagnation of sickle cells within the microcirculation, causing vascular obstruction and dysfunction of the affected tissues and organs, the clinical manifestations are acute onset of bone pain, chest pain and/or abdominal pain, hematuria, etc., known as pain crisis, which may recur during the course of the disease. If a large amount of blood is retained in the liver and spleen, hypovolemic shock will occur due to progressive enlargement of the liver and spleen. Microvascular occlusion causes local tissue hypoxia and inflammatory reaction, which can cause swelling, congestion and pain in the joints of hands and feet, called hand-foot syndrome. In addition, sickle cell anemia may affect the nervous system and cause mental retardation.
Tests
1. In vitro sodium bisulfite sickle test
Add 2% sodium bisulfite or 1% sodium bicarbonate to the blood and make a wet film, a large number of sickle-shaped red blood cells can be seen on the cover sheet, which is helpful for diagnosis.
2. Hemoglobin analysis
Hemoglobin S can be detected by hemoglobin electrophoresis.
3. Blood test
Anemia can be detected by routine blood tests.
4.MRI
MRI signal changes can effectively observe the bone marrow tissue and the extent and severity of involvement of the lesion. When red bone marrow replaces yellow bone marrow, the bone marrow signal in the lesion area is low or medium signal on T1WI and T2WI, similar to the signal of the surrounding muscle tissues and lower than that of the fat tissues. On T1WI, it may show patchy, segmental or widespread low-signal intensity shadows in the metaphysis of the long bones, and may gradually spread to the diaphysis.
Diagnosis
Clinical diagnosis is based on:
1. The patient has jaundice, anemia, hepatosplenomegaly, bone pain and chest and abdominal pain.
2. The patient has a family history of sickle cell anemia.
3. Positive sickle change test.
4. racial susceptibility and high prevalence in the region where they live.
5. hemoglobin analysis reveals hemoglobin S.
Treatment
The disease is treated symptomatically, mainly by blood transfusion and medication, prevention of pain crisis, prevention of infection and hypoxia.
1. When patients have pain crisis and infection, they can be treated with blood transfusion, and attention is paid to monitoring hemoglobin and other indicators.
2. Hydroxyurea can reduce the number of pain crises and the need for blood transfusion, and can also reduce the frequency of episodes of chest syndrome.
3. Folic acid supplementation can reduce increased cysteine levels and improve vascular endothelial function.
4. Patients may have a pre-thrombotic state, which can be minimized by the use of bicoumarin.
5. Bone marrow transplantation, etc. can save lives and improve the quality of survival.
Prognosis
1. Pure heterozygous patients (i.e., those with sickle cell anemia) have a poor prognosis. A few patients survive into adulthood, but usually die before the age of 30.
2. Heterozygous patients (i.e., those with sickle cell) have a better prognosis due to the lower hemoglobin S content in red blood cells, which is usually asymptomatic.
Prevention
Sickle cell anemia is an autosomal dominant disorder and all carriers should undergo genetic counseling. Genetic testing by obtaining fetal cells by amniocentesis is low-risk with reliable results and can be used as a basis for prenatal diagnosis.