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Sickle Cell Anemia

Sickle cell disease is an important disease because it’s by far the most common hematologic disorder in men. One in ten African Americans - in some newer studies the numbers are 1:12 African Americans - and 1:200 whites have sickle cell trait. Overall in the U.S. this results in about 1:400 black births and 1:160,000 white births. In the state of California it ends up being about 1:600 black births. It’s also important to remember that this is a disease that we see in Latinos.

The presentation for sickle cell disease varies with age. Again, what my hope is is that most of these children are picked up before they are symptomatic, because they are picked up on newborn screening. But when children do become symptomatic in the first two years of life the kind of things you tend to see are dactylitis, which is a painful swelling usually of the small bones.

When you think about the manifestations, the acute manifestations of sickle cell disease; this is usually on the basis of intravascular sickling. It can be in response to a number of stresses, and the kind of stresses to think about are cold temperature, infection, change in pH are probably the most common things that are going to cause stresses that are going to induce sickling. This usually results in pain in children, but can also be the basis for things like acute chest syndrome or acute splenic sequestration.

In terms of infections with sickle cell there are only a few key points. The first being that children are functionally asplenic between 6-9 months of age. That’s usually across the board in homozygous sickle cell. There is some variation in some of the heterozygous sickle syndromes like S beta plus thalassemia or SC disease where you might see splenic function continuing for a little bit longer. But it’s important to keep in mind that these children are at profound risk for infections from strep pneumonia and also from H flu. However, if these children are given pneumococcal vaccines, HIB vaccines and prophylactic penicillin.

One question has come up in many people’s practices is, can you ever stop? I think many of us early on said of course not. But I think the answer is probably yes. There probably is, for a substantial number of these patients, there probably is a point in time where you can stop. The national cooperative study was completed a couple of years ago to answer this question.

Acute chest syndrome is an important entity. The reason for that term is it recognizes the inability to differentiate between pneumonia and pulmonary infarction in these patients, and it’s probably not worth trying. The most common causative agents are pneumococcus, Mycoplasma, and H flu. Antibiotics and hydration are the mainstays for treatment of this. Some children do develop oxygen requirements, in fact some actually require intubation and mechanical ventilation in order to support them through. There is plenty of evidence that transfusions for acute chest syndrome really do seem to be beneficial.

This is actually a patient of mine. His initial chest x-ray looked like this and in 48 hours looked like this. He has required intubation and mechanical ventilation at least two or three times in his life, and this concerns me. Because what we now know, from looking at a large group of adult patients, is that anyone who has had acute chest syndrome anytime in the first 20 years of life is at risk for early mortality. So to the extent that we can identify children who have their first episode of acute chest, manage them very closely for other complications of their disease, we hope to reduce their risk for early mortality that may be associated with having had acute chest syndrome.

Incentive spirometry. This is an aside. Happens to be a very effective adjunct to the things we just talked about when treating acute chest syndrome. Something fairly simple. I think what it represents is the fact that many children who have acute chest have enough chest wall pain that they are less inclined to take deep breaths. But certainly if you are able to get them to use the incentive spirometer it seems to shorten their hospitalization and decrease the amount of narcotics that they need to control their pain.

In terms of pain, I think many of you are experts at taking care of this. The mainstays for management of sickle cell pain in the outpatient is primarily hydration and also non-steroidal anti-inflammatories or oral narcotics, such as codeine. There are a few other things that people are trying. Warmth; certainly I find many of my patients tell me that that makes them feel much more comfortable. Getting a good history and physical exam though can not be underscored.

Aplastic crises, or erythroblastopenia is an important complication of not only sickle cell, but really any hemolytic anemia. So if you have anyone with a hereditary spherocytosis they can also get this. These are children who are dependent on high red cell production in order to maintain themselves, so if they have in interruption in that they become precipitously anemic. It can be life threatening. The symptoms that they have are usually related to them having an acute anemia.

Acute splenic sequestration, again, tends to occur in the first two years of life. It can occur later in patients who have SC disease. The typical findings are again are those of acute blood loss or hypovolemic shock, such as pallor, tachycardia, lethargy and the parents may tell you that they have some abdominal fullness. Many of the minor episodes are self-limited however that patient can have a major episode that can be fatal.

Treatment typically is with plasma expanders. Again, I don’t try to transfuse them back up to their normal because many of these children will eventually re-mobilize some of those red cells out of their spleen back into circulation. So you really don’t want to have given them a normal hemoglobin and then when they re-mobilize having them to overshoot and develop problems on that basis. If patients have recurrent sequestrations, chronic transfusions seem to be effective in getting them to where they are a little bit older and out of the period where they are at highest risk. Splenectomy however is sometimes the only way to deal with major episodes.

The initial evaluation of sickle cell; this sort of goes back to things we talked about initially, with evaluation of anemias. A hemoglobin electrophoresis is probably the most common test available in the community for diagnosing them, and this is what it looks like. It is simply looking at the total proteins in a red cell and then looking at them as they migrate on a gel, and this difference in the migration pattern should allow you to differentiate between things.