Transcription
Sickle cell disease: port for diagnosis and treatment. We have discussed before an introduction, pathophysiology, and clinical picture of sickle cell disease. Now, we have diagnosed and will discuss how to manage sickle cell disease. But first, let me tell you there is no cure other than stem cell transplant, which is a major surgery with a lot of risk. Most of the time, we are talking about management—how to reduce symptoms. But the ultimate cure is again stem cell transplant or bone marrow transplant.
But first, let me answer the quiz from the last video. The most common cause of death in sickle cell disease in children is infection. The most common cause of death in adults with sickle cell disease is acute chest syndrome. The causative organism of meningitis in children? Strep pneumo is the most common. Most common cause of organism of bacteremia? Strep pneumo. Most common cause of organism of osteomyelitis? Salmonella. Second most common is staph aureus. Salmonella has exceeded staph aureus because there is no spleen, and Salmonella is an encapsulated organism. The most common type of hemoglobin is hemoglobin S. The reason to seek medical attention is pain; the vaso-occlusive crises are very painful.
How to diagnose this ugly disease prenatally and postnatally? Prenatally, while the baby is still in the mother's womb, you can do DNA-based testing such as PCR or allele-specific hybridization. There are two methods to obtain the DNA: either by chorionic villus sampling or amniocentesis. I've made a video before explaining CVS, so you can check it out. Postnatally, you have several methods. On CBC, how about the blood cell count? Usually low. How about hemoglobin and hematocrit? Of course, they are low because this is anemia. MCV is usually normal; it's a hemolytic anemia. Reticulocytes—oh, this is cool—reticulocytes are usually increased because there is hemolysis, and the bone marrow will respond by increasing production of red blood cells. Reticulocytes are the baby red blood cells. However, if you have parvo B19, if you have aplastic crisis, the reticulocyte count will be decreased. Fine. What else can you do? Something called a sickle cell screen by adding sodium metabisulfite, which will decrease the oxygen tension, forcing the cells to sickle. If there is hemoglobin S, when the cell sickles, you can see that the test tube is now very turbid; it's not clear. Third, you can use a peripheral smear or a blood film. When you order it and look under the microscope, you will see sickle cells. Please pay attention: sickle cells are only seen in sickle cell anemia, but not in sickle cell trait—huge difference. Sickle cell anemia has sickle cells; sickle cell trait, no sickle cells. Really, yes. Many students will confuse this point. Again, sickle cell disease with hemoglobin SS: there are sickled cells under the microscope. Sickle cell trait with hemoglobin AS, the carrier, they have no sickled cells; the red blood cells are normal. It's a trait; it's not a disease; it's a carrier state. I hope that's clear. You can use gel electrophoresis; this is a definitive method. It will detect the hemoglobin S, and by definition, sickle cell disease has hemoglobin S.
How about the ESR? So normally, the erythrocyte sedimentation rate—the red blood cells in the test tube will attach together, forming rouleaux, and they will precipitate. Here is the sedimentation—erythrocyte sedimentation rate. But now, in sickle cell disease, this abnormal shape of the red blood cell will make rouleaux formation impossible. How can you form rouleaux when your red blood cells are in this crazy shape? You can't. So the ESR will be low, i.e., the red blood cells will take a longer time until they precipitate, so the ESR will be low. Also, keep in mind in sickle cell disease, neutrophilia is common.
Now let's talk management. Again, there is no cure for sickle cell disease except bone marrow transplant, and I don't think that kids with sickle cell disease or their parents would love that they undergo bone marrow transplant. So how to manage it? Daily folic acid in this disease, as well as any other hemolysis; there is a rapid turnover of cells, so you need folate because it's consumed rapidly. For the aplastic anemia, you give antibiotics and you vaccinate. Which antibiotic? Penicillin V. And you give penicillin V until the kid reaches five years of age. Vaccinations: there are five vaccinations that you should give to all patients with sickle cell disease: pneumococcus, meningococcus, Haemophilus influenzae (which is a bacterial influenza, not a virus), and Hep B. For the vaso-occlusive crisis: first, aggressive rehydration. And one of the complications of sickle cell disease that I forgot to mention last video is priapism. Okay, and to treat priapism, we first rehydrate, treat the pain—they are painful—nonsteroidals, but if it's severe, give opioids such as morphine. Antibiotics, sure. How about increasing hemoglobin F, because hemoglobin F is anti-sickling, by giving hydroxocobalamin, aka hydroxyurea? Remember, anything that will shift the oxygen dissociation curve to the right is pro-sickling; anything that shifts the curve to the left is anti-sickling. Hemoglobin S sickles, but hemoglobin F is anti-sickling because it shifts the curve to the left. Now you understand. Last, you can do transfusion, especially exchange transfusion, in severe cases of sickle cell disease. Patients with sickle cell disease should be screened for strokes by doing a transcranial Doppler ultrasound. We start doing this at age two until 16 years of age; we repeat the test every one or two years. Check for retinopathy by doing a fundus exam starting at age 10.
That's it for sickle cell disease. I hope now you know everything about this disease. It's very high yield for any medical exam, whether medical school, certification, recertification—whatever—you will need to know everything about sickle cell disease. That's it for today. I'll see you in the next video. Stay tuned. I really do appreciate you taking time to watch this video, and I'll see you next time.