Sideroblastic Anemia and TIBC levels

[phd89]

So Pathoma says that the TIBC will be dec in Sideroblastic Anemia whereas FA says the TIBC is normal. Can somone expain which one it is and why. I could understand a dec in TIBC going with pathoma's explanation but could FA be right here ie. normal?

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[dragon529]

My understanding is that towards the beginning of sideroblastic anemia, TIBC can be in the normal range since not much iron is locked up in the mitochrondrias of RBC. Later in the disease, there's so much ferritin that TIBC will decrease. I think it's one of those things that values vary according to the stage of the disease....

 

[OveractiveBrain]

So Pathoma says that the TIBC will be dec in Sideroblastic Anemia whereas FA says the TIBC is normal. Can somone expain which one it is and why. I could understand a dec in TIBC going with pathoma's explanation but could FA be right here ie. normal?

The typical pattern of a sideroblastic anemia is NORMAL iron studies, except an elevated iron. If you see NORMAL IRON PANEL or ELEVATED IRON, jump to Sideroblastic anemia. Anything can be anything, and the only way to diagnose the disease is with a biopsy, so look for the typical patterns to get the test question right!

 

[Phloston]

I have annotated from Kaplan QBank that, in sideroblastic anaemia, serum iron is increased, TIBC is decreased and ferritin is normal.

On the USMLE, I'd go with this pattern. Iron builds up because the mitochondria can't utilize it, so TIBC decreases.

 

[Charles_Carmichael]

I have annotated from Kaplan QBank that, in sideroblastic anaemia, serum iron is increased, TIBC is decreased and ferritin is normal.

On the USMLE, I'd go with this pattern. Iron builds up because the mitochondria can't utilize it, so TIBC decreases.

Why would ferritin be normal? I thought ferritin was increased in all iron-overloaded states. Does this have to do with what "stage" of the disease process you're in?

The way I learned sideroblastic anemia: TIBC is decreased while serum iron, serum ferritin, and percent saturation all increase.

 

[Phloston]

Why would ferritin be normal? I thought ferritin was increased in all iron-overloaded states. Does this have to do with what "stage" of the disease process you're in?

The way I learned sideroblastic anemia: TIBC is decreased while serum iron, serum ferritin, and percent saturation all increase.

Look at p.385 of FA at the lead poisoning column for iron. The mechanism is the same.

 

[thecalccobra]

Hmm, I just checked Pathoma and Goljan and both have increased Ferritin in sideroblastic anemia.

Can anyone explain why Ferritin levels are normal in lead poisoning? I never thought of it that way.

 

[Phloston]

Hmm, I just checked Pathoma and Goljan and both have increased Ferritin in sideroblastic anemia.

Can anyone explain why Ferritin levels are normal in lead poisoning? I never thought of it that way.

As far as I'm aware, ferritin increases when overall body iron is increased (e.g. increased absorption with primary haemochromatosis or forced parenteral overload with secondary haemochromatosis) or when the cells simply can't release it; in the case of the latter, hepatic up-regulation of hepcidin production prevents liberation of iron stores (anaemia of chronic disease).

With Pb-poisoning or sideroblastic anaemia, there isn't an overall systemic excess of iron nor is there impaired release of it; it's just floating around because it's not properly being incorporated into haeme.

 

[Charles_Carmichael]

Sideroblastic anemia DOES produce an iron-overloaded state. There should be an increase in ferritin. Pathoma and RR both state this and even FA shows an increase in ferritin (look at page 381 Pholston).

The only thing I'm unsure of is regarding TIBC levels. FA says they're normal, but I think that's only the case earlier on in the disease process. As the sideroblastic anemia progresses, you should see a decrease in TIBC.

 

[mayn]

Sideroblastic anemia should have increased ferritin. I would think, like most people here already, that the TIBC being either normal/low would be a matter of time (like early iron deficiency being normocytic, rather than microcytic).

As time passes and the mitochondria fails to incorporate iron into heme, the iron accumulates in the RBCs and bone marrow macrophages. The iron eventually leaks out into the serum, increasing: a) serum iron, b) iron percent saturation and c) ferritin
(resulting in iron overloaded state).

TIBC will consequently be decreased.

Similar lab findings will also be in hemochromotosis (the other iron overloaded state)

 

[Phloston]

That's so weird. Kaplan QBank went into the specifics, but they didn't mention the increased ferritin; they just said increased serum iron and decreased TIBC. I would think sideroblastic anaemia would follow the same pattern as Pb-poisoning (p. 385 shows normal ferritin). Could you please explain why the ferritin would be increased in the former but not the latter?

 

[mayn]

I.. honestly don't know. As far as I know in all forms of sideroblastic anemia (alcohol/lead poisoning/B6 def) ferritin should be increased, with a decreased TIBC.

Goljan's book says specifically increased ferritin for lead poisoning, and also for sideroblastic anemias. I would've thought it might be an error in FA, but you said Kaplan qbank has it as 'normal' too.

Also.. the way I've always understood it, is TIBC and ferritinare supposed to be inversely proportional. Andtransferrin and TIBC are directly proportional.

Decreased ferritin increases synthesis of transferrin (increasing TIBC); such as seen in iron deficiency anemia.
Increased ferritin would cause the opposite; decrease synthesis of transferrin (decreased TIBC); seen in anemia of chronic dz and iron overloaded states.

 

[withrye]

The way I've understood it, all sideroblastic anemias (Pb poisoning, ALA synthase deficiency, copper deficiency, etc) share the same profile. High ferritin, normal to low TIBC. You're constantly consuming Fe, and without a reliable way to dump Fe the only real way to manage it is to not take it up in the first place.

With all sideroblastic anemias the Fe is trapped in the mitochondria, leading to improper sensing of serum Fe levels, leading to improper overabsorption of Fe. You're now in a temporary state of high ferritin, low serum Fe. As you overload the cells they rupture, spilling Fe into the blood, raising serum Fe, keeping ferritin high, and lowering TIBC (given enough time). In short, I don't think Pb poisoning is different than the other sideroblastic anemias (in terms of iron studies).

 

[Phloston]

Thanks for the input, guys.

In this case, particularly based on what Goljan's RR apparently says (I could double-check myself, but I find the dust that it's collecting on my shelf fairly attractive), I'd be inclined to go with increased serum iron, decreased TIBC and increased ferritin, for both Pb-poisoning and sideroblastic anaemia, on the real deal.

 

[Phloston]

Just thought about it some more:

Considering Goljan says increased ferritin for Pb-poisoning but FA says normal, I would go with normal vs increased for acute vs chronic, respectively. In sideroblastic anaemia, that is inevitably a chronic process, so increased is right.

On the USMLE, the acute vs chronic Pb situation might take form as a child with GI bleeding after the family moves into a new house (acute) vs a guy who's been working at a bullet-making factor for a decade who has dementia and wrist drop (chronic). Then we could say normal vs high ferritin.