FA 14 and FA 15 discrepancy (Subacute Combined Degen)

[Silverish]

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FA 14 says Subacute combined degeneration can be caused by Vit B12 def or Vit E def.
FA 15 says Subacute combined degeneration can be caused by only Vit B12 def.
Uworld has a question based on Subacute combined degeneration being caused by Vit E def.

Has anyone seen a question on STEP based on Vitamin E deficiency causing subacute combined degeneration?

 

[malin]

Even if someone has, they technically aren't allowed to post it on this forum (post might get deleted, they might get disciplined, etc). You could maybe google this topic and see what the literature says for both vitamins, but otherwise I would just assume both cause it. Not really sure why First Aid took it out.

Some of the UWorld questions pop up word for word on Step 1. If it popped up in UWorld, it could have been on a previous Step 1, or is on current Step 1 exams. Or they might retire that question from UWorld and have it appear on future Step 1s. Of all 3 of those resources, UWorld is most reliable for Step 1. So maybe just assume that both vitamins cause it. I don't think Step 1 would ever have both answer choices in the same question.

 

[seminoma]

FA 14 says Subacute combined degeneration can be caused by Vit B12 def or Vit E def.
FA 15 says Subacute combined degeneration can be caused by only Vit B12 def.
Uworld has a question based on Subacute combined degeneration being caused by Vit E def.

Has anyone seen a question on STEP based on Vitamin E deficiency causing subacute combined degeneration?

Both. E has hemolytic anemia. B12 has megaloblastic anemia.

 

[Silverish]

Thanks for the heads up @malin.
Thanks for the answer @seminoma

 

[DrPicard]

I might be mistaken about this since I'm still on my first read through, but Goljan mentions B12 deficiency affecting the dorsal column + lateral CS tract + the spinocerebellar tract. Vit E affects the dorsal column and and lateral CS, but not the spinocerebellar, so thats one difference.

And of course B12 has megaloblastic and E hemolytic (with acanthocytes) anemia.

 

[scoKraz4]

Don't get hung up on what FA says. If you are unsure about something go research it a little. Uworld is solid cause it often has sources to back it up. FA will pick and choose things based on what the editors feel is important.

 

[worldbeater]

Silverfish, what's the UWorld question # you had with subacute combined degeneration and Vitamin E?

I got a question wrong with subacute combined degeneration, and the answer was Vitamin B12 deficiency (Q#65)

 

[Phloston]

B12 deficiency causes the classic SCD (spinocerebellar, corticospinal, dorsal columns).

Vitamin E deficiency can lead to hemolysis and definitely neurological dysfunction as well. It was removed from FA because of the overwhelming number of errata submissions and the confusion it was causing. And the picture often isn't the classic SCD. That term SCD is essentially synonymous with neuro dysfunction secondary to B12 deficiency if it were ever mentioned in a medical setting.

On the USMLE:

If you get neuro dysfunction in any capacity and no other helpful information (and it's not an INH-B6 question), the answer is B12 deficiency.

If you get neuro dysfunction and hemolysis, the answer is vitamin E deficiency.

If you get neuro dysfunction and they say anything about high serum methylmalonic acid/methylmalonyl-CoA, the answer is B12 deficiency.

And of course any mention of increased MCV and/or hypersegmented neutrophils with neuro dysfunction = B12 deficiency.

 

[Silverish]

Silverfish, what's the UWorld question # you had with subacute combined degeneration and Vitamin E?

I got a question wrong with subacute combined degeneration, and the answer was Vitamin B12 deficiency (Q#65)

Firstly, its SilverISH! LOL
Secondly, (and again LOL), Uworld must have very recently changed this question. I just checked it.
It was vitamin E before. I swear it.
Its kinda funny. You can search "vitamin e" and Q 65 will come up (even with no mention of vitamin e in the explanation). HMPH.

 

[worldbeater]

Haha my mistake Silverish, thought there was a "f' in there somewhere.

Just searched "Vitamin E" and your right Q65 came up as the third result. Very odd, but will remember B12 as the answer now.

 

[Silverish]

UPDATE: I recently had a question about a CYSTIC FIBROSIS patient with ataxia and peripheral nerve problems! annnddd guess what the answer was!
Vitamin E deficiency.
FA, u try to fack on me?! I keel yew!