sickle cell anemia
Introduction
Introduction to sickle cell anemia Sickle cell anemia is the first molecular disease discovered in the world in 1949, which led to the era of disease molecular biology. Its molecular pathology is a single base mutation in the gene. The sixth codon of the normal gene is GAG, which is compiled with glutamic acid. After mutation, it becomes GTG, and the proline is compiled. This single amino acid substitution forms HbS. Therefore, deoxidation can make the red blood cells stiff and deform, and become a sickle-shaped, hence the name. basic knowledge The proportion of illness: 0.04% Susceptible people: no special people Mode of infection: non-infectious Complications: femoral head necrosis osteomyelitis septic arthritis sickle cell anemia hyperuricemia
Cause
Cause of sickle cell anemia
Cause (40%):
Autosomal dominant hereditary disease. The initial stage of red blood cell transmutation is reversible, and oxygen can reverse the transmutation process, but when the transmutation has seriously damaged the red blood cell membrane and the red blood cells lose potassium ions and water, the transmutation becomes irreversible, even if the cells are placed Under aerobic conditions, the red blood cells remain scorpion-like.
Prevention
Sickle cell anemia prevention
The disease has a poor prognosis and lacks effective treatment, so it should focus on prevention, promote eugenics, pre-marital and prenatal examinations, currently using polymerase chain reaction (PCR) and oligonucleotide probe (ASO) methods, or using PCR and The restriction endonuclease fragment length polymorphism (RFLP) method allows prenatal diagnosis in early pregnancy to prevent the birth of homozygous children.
Complication
Sickle cell anemia complications Complications femoral head necrosis osteomyelitis septic arthritis sickle cell anemia hyperuricemia
In early childhood cases, hand-foot syndrome can be complicated, 20% of patients with HbSS disease can develop femoral head necrosis; osteomyelitis and septic arthritis; more than 40% of patients with sickle cell anemia can have hyperuricemia Symptoms, patients with sickle cell anemia can occasionally have chronic synovitis.
Symptom
Symptoms of sickle cell anemia Common symptoms Hyperuricemia refers to (toe) bone infarction gallstones soft tissue swelling osteoporosis
Clinical symptoms are rare within 6 months after birth and are usually diagnosed within 2 years of age. Most children with homozygous HbSS disease die before the age of 7 years. Clinical symptoms include hemolysis, anemia and vascular occlusion. Splenomegaly is seen in childhood. Due to repeated infarction and diffuse fibrosis, atrophy, functional spleen, seen in young children, making patients susceptible to infection, especially Salmonella infection, infection and folic acid deficiency can lead to low erythropoiesis, aplastic crisis, leg Ulcer is a common manifestation of the skin. Due to long-term anemia, the heart is often enlarged. Cardiac and pulmonary insufficiency can occur in the elderly, and gallstones and cholecystitis are also common complications due to long-term massive hemolysis. In addition to the above-mentioned manifestations, there are bone and joint lesions. :
1. Painful crisis: It is the most characteristic musculoskeletal complication. It is most common in the proximal joint area of long bones. It can also be seen in the back, ribs, and even the abdomen. Pain often occurs in many parts, sometimes symmetry. Local swelling may occur, especially in the humeral epiphysis. One or more joints may be secondary infections. The duration of uncomplicated pain crisis is generally less than 2 weeks. The factors that induce pain crisis are infection, cold, pregnancy, Emotional stress and high altitude travel, the incidence of pain crisis in female patients is significantly lower than that of males. The incidence of male patients aged 15 to 25 is the highest, and those with frequent pain crisis of 20 years and older have high mortality.
2. Dactylitis (dactylitis): In young children, vascular occlusion often occurs in the back of the hands and feet, causing finger inflammation, also known as hand-foot syndrome, clinical manifestations of hand and foot non-concave Swelling with pain, symptoms can be improved after 1 week, but often recurrence, usually without leaving sequelae, but sometimes central necrosis of the bone can lead to early healing of the finger (toe) and shortening of the toe.
3. Osteonecrosis: 20% of patients with HbSS can develop femoral head necrosis, which can not be differentiated from pain crisis at the beginning. However, after 2 weeks, the pain does not disappear, the walking is aggravated, and the rest is improved, suggesting that there is a merger. Bone necrosis, the prognosis is related to the age of the patient. The prognosis of adults is worse than that of children. The incidence of femoral head necrosis is not common in patients with HbSC and HbS--globin-producing anemia under 15 years old, and the incidence of elderly cases Higher, osteonecrosis is also seen in other joints, especially the shoulder joint, which is characterized by pain and limited abduction rotation.
Examine
Sickle cell anemia check
1. Peripheral blood: Hemoglobin is 50 ~ 100g / L, further reduced in crisis, reticulocyte count is often more than 10%, red blood cell size is uneven, more staining, basophilic point cells increase, visible nucleated red blood cells Target red blood cells, abnormal red blood cells, Howell-Jolly bodies, sickle-shaped red blood cells are rare, if found, it is helpful for diagnosis, usually using "mutation test" to check for the presence or absence of sickle cells, red blood cell osmotic fragility is significantly reduced, White blood cell and platelet counts are generally normal.
2. Bone marrow: Significant hyperplasia of the erythropoiesis, but proliferative hypoplasia in the crisis of aplastic disorders, there are giant juvenile cells in the megaloblastic crisis.
3. Serum bilirubin: mild to moderate increase, significantly increased in the hemolytic crisis, although the hemolysis of this disease is mainly extravascular hemolysis, but there is also intravascular hemolysis.
4. Plasma haptoglobin is reduced and plasma free hemoglobin may be increased.
5. Red blood cell half-life determination: It shows that the red blood cell survival time is significantly shortened to 5 to 15 days [normal (28 ± 5) days].
6. Hemoglobin electrophoresis: It shows that HbS accounts for more than 80%, HbF increases to 2% to 15%, HbA2 is normal, and HbA is absent.
Diagnosis
Diagnosis and diagnosis of sickle cell anemia
diagnosis
The diagnosis of this disease is not difficult. It is important to consider the possibility of the disease without missing the disease. According to race and family history, the mutation test is positive. Hemoglobin electrophoresis shows that the main component is HbS, and then combined with clinical manifestations, ie Can be clearly diagnosed.
Differential diagnosis
Repeated joint pain and obvious heart enlargement are easily misdiagnosed as rheumatism. Acute abdominal pain is easily misdiagnosed as acute abdomen. Osteonecrosis can be misdiagnosed as bacterial osteomyelitis. Obvious jaundice can be confused with other causes of jaundice, and should be identified.
