Methemoglobin and Heinz Bodies

[DoctorDork]

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So I'm studying for the Step I boards with first aid and I learn that methemoglobinemia is when the iron on Hb is in its Fe3+ form instead of its normal O2 binding state of Fe2+. Then I go on to learn about Heinz bodies and first aid says' heinz bodies- oxidation of iron from ferrous (Fe3+) to Ferric (Fe2+) form leads to denatured Hb precipitation and damage to RBC membrane. Leads to the formation of bite cells. Seen with alpha thalassemia and G6PD deficiency. "
So my questions is why don't we see Heinz bodies whenever a person is suffering from methemoglobinemia? Why is it only these 2 conditions? Please help explain this concept to me!!

 

[FlowLimited]

So I'm studying for the Step I boards with first aid and I learn that methemoglobinemia is when the iron on Hb is in its Fe3+ form instead of its normal O2 binding state of Fe2+. Then I go on to learn about Heinz bodies and first aid says' heinz bodies- oxidation of iron from ferrous (Fe3+) to Ferric (Fe2+) form leads to denatured Hb precipitation and damage to RBC membrane. Leads to the formation of bite cells. Seen with alpha thalassemia and G6PD deficiency. "
So my questions is why don't we see Heinz bodies whenever a person is suffering from methemoglobinemia? Why is it only these 2 conditions? Please help explain this concept to me!!

First off, ferrous is Fe2+ and ferric is Fe3+. I don't know why you wouldn't see Heinz bodies in people with methemoglobinemia. I'd think you would.

 

[WellWornLad]

Leads to the formation of bite cells. Seen with alpha thalassemia and G6PD deficiency. "
So my questions is why don't we see Heinz bodies whenever a person is suffering from methemoglobinemia? Why is it only these 2 conditions

We do see Heinz bodies with methemoglobinemia. I don't think a-thalassemia and G6PD were meant to be an exhaustive list.

 

[Rendar5]

It's kinda like that House episode form the first season when the girl turned out to be XY androgen insensitive and had a paraneoplastic syndrome from testicular cancer. The clue that she was really XY? scant pubic hair on a pelvic exam...Sure you might have it, but why would you even look for it when you could've just seen the complete lack of a cervix and uterus on pelvic exam.

It's the forest for the trees. Someone's coming in with methemoglobin, the answer's not gonna be in the manual slide even if a clue's there, you're gonna look at the blood gas. Whereas when someone's anemic, you're gonna look at the slide, and see Heinz bodies and evidence of G6PD hemolysis or evidence of a thallasemia.

Put this under the cool factoid list, but spare it from your clinical reasoning skills unless u're gonna be a hematologist =p

 

[bydotte]

my acronym is "us 2 met eric" ferrous is +2, methemoglobin is ferric.

 

[BOOURNS]

I can't answer your question, but I can say with some confidence that you are wasting your time thinking about this stuff if a good score on step1 is your goal...

 

[DocPsychosis]

Also, going from +2 to +3 state is oxidizing, not reducing.

 

[bodonid]

this may be obvious, but methemoglobin is caused by oxidation of iron, but heinz bodies are not. heinz bodies are caused by oxidation of amino acids (cystine?) in hemoglobin. Two different things, the only tie between them is that they are both caused by oxidations. right?

 

[arachnoid]

Heinz bodies form whenever hemoglobin is damaged and consequently destroyed, not only when it's oxidized.