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Sideroblastic Anemias

Sideroblastic anemia. What are the clinical and laboratory findings in sideroblastic anemia? Well, classically we think of it as microcytic. In fact, more often it is a mixed picture. It’s a dimorphic picture and in many patients it actually may be macrocytic. So the MCV that you see in such a patient can be low, normal or high. Even though classically, particularly in the past, it has been lumped among the microcytic anemias. The disturbance in terms of hematopoiesis takes the form of ineffective erythropoiesis. And ineffective erythropoiesis means that the bone marrow is working overtime making red cell precursors and if you look at the bone marrow biopsy it is loaded with red cell precursors. But most of them don’t survive until adulthood.

Now the most common sideroblastic anemias that you are going to see are not the hereditary ones. And I should point out, by the way, that while we talk about hereditary disorders a lot of them don’t present until people are young adults. In fact, it’s being recognized more and more that there are some where the recognition is delayed until middle age or even when people are in Far and away, the most common sideroblastic anemias that we see are in the primary or clonal disorders, and most specifically the myelodysplastic syndromes.

A very interesting set to think about, and it’s nice to think about these, because these are by and large treatable, are the secondary acquired. We can put them into several categories. The ones that are best known are toxins and drugs.

The anti-tuberculin drugs typically cause - particularly in the slow acetylators, we give anyone who take INH we give them 50 mg of pyridoxine a day simply on a preventive basis to cover those who are slow acetylators; 50 mg of pyridoxine is not toxic. These are fairly standard. Chloramphenicol is a drug that we don’t use much but is actually a very classical inducer of … it’s a mitochondrial poison in humans.

Another interesting one is some deficiency states, and particularly copper deficiency. It was first described in people who were taking TPN and they became copper depleted and one of the manifestations was sideroblastic anemia. One of the interesting ways we see it now are people who take high doses of zinc. And not that high a dose.

Okay, I will close then by going through, what are the things to do if you’ve identified sideroblastic anemia? I think sideroblastic anemia is more common than we think. In some settings it’s pretty obvious. If a patient presents to you with what turns out to be a myelodysplastic syndrome. In some, though, you sort of have to go hunting for it. One of the things I want to leave with you is think about it if you see people with just high iron levels. Although you need to do the bone marrow to make the diagnosis. Well, what do you do? If at all possible you reverse the underlying cause, obviously.

The kinds of doses we use are fairly high ones. Usually start off with about 200 mg a day. You usually have to give it at least a month or two before you call that trial off, and if it’s successful then you try to titrate the doses down. Because, while 200 mg a day of pyridoxine isn’t really the kinds of doses that produce the neurological toxicity that you can see with pyridoxine, never-the-less you like not to have it at such a high dose. We try to titrate it down to the lowest dose that will keep the patient non-anemic. Transfusions; here, sometimes you have no choice, but again one has to use it only if necessary.

Now what other things are you left with? Well, you often do sort of support kinds of things. Many of the patients - because iron overload sometimes is the way the patient will eventually die, and that’s preventable - so in many patients you have to decide which one it’s appropriate for, iron chelation should be started at diagnosis. Some people have gone so far as to suggest phlebotomy and what you think about is it’s a little humorous to use phlebotomy in a patient with anemia, but you can do it.

The last thing one has to think about is if you’ve diagnosed what may be a hereditary disorder, screen the family even if they are asymptomatic. You may find uncle Charley who is 50-years-old has sideroblastic changes that might not present until ten years later.