What protein defective in Spherocytosis?

[Captopril]

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Goljan says ankyrin defect in most cases (spectrin is only minor)

On UW, all Q's about spherocytosis give spectrin defect as the molecular cause of the structure abnormality. No mention of ankyrin.

So which one is correct if it ever comes up as a question: ankyrin or spectrin?

PS - I realize that elliptocytosis is due to spectrin according to Goljan, so my question is specifically pertaining to the spherocyte defect.

 

[beezel]

According to Robbins PBD (7th ed), HS can be caused by various mutations in ankyrin, band 3, spectrin, or band 4.2, but the MOST COMMON cause of autosomal dominant HS is a mutation in ankyrin. However, the Kaplan books say it's a defect in spectrin.

I usually defer to Robbins, so I if I had to choose between the two and the stem indicated it was AD inheritance, I would go with ankyrin. I doubt they would give both options though, that would be pretty unfair.

 

[Captopril]

According to Robbins PBD (7th ed), HS can be caused by various mutations in ankyrin, band 3, spectrin, or band 4.2, but the MOST COMMON cause of autosomal dominant HS is a mutation in ankyrin. However, the Kaplan books say it's a defect in spectrin.

I usually defer to Robbins, so I if I had to choose between the two and the stem indicated it was AD inheritance, I would go with ankyrin. I doubt they would give both options though, that would be pretty unfair.

Yeah I would assume they wouldn't delve into topics that are disputed like that. I normally wouldn't even ask, but a lot of times I see SDNers asking for clarification on similar minor discrepancies, so just thought I would do it too just in case.

Thanks for the response...I'd probably go with ankyrin just because of the Goljan + Robbins endorsement.

 

[Flaxmoore]

Put a gun to my head and ask, and I say ankyrin. Spectrin plays a role, but less than ankyrin.

 

[durfen]

Put a gun to my head and ask, and I say ankyrin. Spectrin plays a role, but less than ankyrin.

it's actually either/or I believe. I hate structural proteins anyway.

 

[ObamaCare]

The answer is: Step I doesn't care. Anything beyond Goljan/UW/Robbins Review info is overkill and a waste of your energy.

 

[Mortal_Lessons]

it's actually either/or I believe. I hate structural proteins anyway.

Remember structural protein disease is typically inherited in an autosomal dominant fashion, whereas enzyme disease is more often inherited in a recessive manner.

 

[Captopril]

The answer is: Step I doesn't care. Anything beyond Goljan/UW/Robbins Review info is overkill and a waste of your energy.

It's within the scope of all of these, since it was on a UW question, in RR Path by Goljan, and was asked in Robbins Review.

 

[ObamaCare]

It's within the scope of all of these, since it was on a UW question, in RR Path by Goljan, and was asked in Robbins Review.

Are you sure? The practice questions on spherocytosis are always presented with a similar clinical scenario, and then a picture of the characteristic RBCs or a lab value of increased MCHC. If the question is what the most likely defect, the answer choices always includes EITHER spectrin OR ankyrin OR "structural protein".

They'll never make you differentiate ankyrin vs. spectrin. It's akyrin, btw. Goljan just wanted to hammer in the memory tool in his audio "SPherocytosis and SPectrin".

I understand the concern though... I had such a specific pharm question on my exam I thought they'd never ask. I just can't picture an ankyrin vs. spectrin question.

 

[Captopril]

Are you sure? The practice questions on spherocytosis are always presented with a similar clinical scenario, and then a picture of the characteristic RBCs or a lab value of increased MCHC. If the question is what the most likely defect, the answer choices always includes EITHER spectrin OR ankyrin OR "structural protein".

They'll never make you differentiate ankyrin vs. spectrin. It's akyrin, btw. Goljan just wanted to hammer in the memory tool in his audio "SPherocytosis and SPectrin".

I understand the concern though... I had such a specific pharm question on my exam I thought they'd never ask. I just can't picture an ankyrin vs. spectrin question.

Yeah you're right, the question never actually asks you to differentiate. Just thought I'd have all bases covered just in case. As my Physio instructor at Kaplan said: "Why do the USMLE people ask you these things? Because they are BASTARDS".

 

[McGillGrad]

Yeah you're right, the question never actually asks you to differentiate. Just thought I'd have all bases covered just in case. As my Physio instructor at Kaplan said: "Why do the USMLE people ask you these things? Because they are BASTARDS".

If they do ask you to tell the difference, it is one of those questions that differentiate between a 220 and 240 (if you get enough of these types right).

As simple as it may seem, the way to be above average on the step is to simply get right what everyone gets right and then get right the ones most people get wrong. So if no one really knows something and you get it wrong, no harm done. But if you get it right, then all the better for you.

 

[eduro25]

Actually Goljan puts the ankirin deffect of spherocytosis as a High Yield Margin note in its second edition RR Path book , which means probably will come on the exam.

Just my two cents. 🙂

 

[doogoshly]

just any protein that is involved in maintaining the RBC shape. so it could be any of those listed, it just happens that ankyrin is the most commonly affected (i think). so just know why you get sphero and have the spectrin or ankyrin in your head.

 

[tavankitsingh]

Harrison's 17th edition quotes ankyrin defect as the most common cause of spherocytosis and defect in alpha spectrin as the most common cause of elliptocytosis...

 

[Captopril]

Harrison's 17th edition quotes ankyrin defect as the most common cause of spherocytosis and defect in alpha spectrin as the most common cause of elliptocytosis...

Yup, same thing big G (Goljan) says in Rapid Review. Awesome that RR Path and Harrison's are basically at the same level of detail orientation.

 

[TexasTriathlete]

I think Goljan says spectrin on the audio.

 

[a winner is you]

Doesn't matter, just remember both. They'll never make you choose between ankyrin and spectrin, because both answers are correct.

 

[Durgsheel]

here is my two cents
mneumonic for HS-
JAAMON - JAAMON (based in the the lovely Penelope Cruz's film)

J jaundice
AAnkyrin defect, spectrin also band 3
AAplastic anemia
M Increase MCHC
O osmotic fragility test
N Normocytic anemia

also get gallstones from calcium bilirubinate because of increased concentration of conjugated Bili in bile

tx --> splenectomy