NBME6 help with a Q

[step1april2013]

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I've tried searching the forum for a good answer, but it seems I can't find one. Someone please explain this to me.

A 37-year-old woman develops pancytopenia after exposure to a benzene-containing agent. Tissue obtained on a bone marrow biopsy is most likely to show replacement of normal hematopoietic cells by which of the following cells?

A) Adipocytes
B) Lymphocytes
C) Monocytes
D) Osteoblasts
E) Reticuloendothelial cells


I put B as the answer, but it was wrong.

 

[preDoGuy24]

I would have put A, aplastic anemia can occur from benzene exposure, and loss of hematopoietic cells and increased adipose is a consequence of that.
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[calvnandhobbs68]

Yeah I'm gonna say A too. I'd think aplastic anemia with pancytopenia.

 

[step1april2013]

I would have put A, aplastic anemia can occur from benzene exposure, and loss of hematopoietic cells and increased adipose is a consequence of that.
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okay makes sense.

On an unrelated note...In order to classify a disease as having mitochondrial inheritance does the mother have to express the disease (show the phenotype) in order to pass the disease down to her offspring or can the disease be hidden and still be passed down? (I guess what I'm saying is does the mitochondrial inheritance show a kind of autosomal dominant inheritance, where every affected person shows the phenotype)

 

[Jonari]

i think i understand why you wrote lymphocytes, because lymphocytes are the earliest cells affected with whole body radiation, but WBR doesn't cause pancytopenia. here's a table from goljan's rapid review for causes of aplastic anemia...

 

[step1april2013]

i think i understand why you wrote lymphocytes, because lymphocytes are the earliest cells affected with whole body radiation, but WBR doesn't cause pancytopenia. here's a table from goljan's rapid review for causes of aplastic anemia...

very nice thank you

Yeah I'm gonna say A too. I'd think aplastic anemia with pancytopenia.

I agree

On an unrelated note...In order to classify a disease as having mitochondrial inheritance does the mother have to express the disease (show the phenotype) in order to pass the disease down to her offspring or can the disease be hidden and still be passed down? (I guess what I'm saying is does the mitochondrial inheritance show a kind of autosomal dominant inheritance, where every affected person shows the phenotype)

Can someone help me with my above question

 

[Jonari]

okay makes sense.

On an unrelated note...In order to classify a disease as having mitochondrial inheritance does the mother have to express the disease (show the phenotype) in order to pass the disease down to her offspring or can the disease be hidden and still be passed down? (I guess what I'm saying is does the mitochondrial inheritance show a kind of autosomal dominant inheritance, where every affected person shows the phenotype)

mitochondrial DNA shows variable expression so different people are going to show the severity at different levels...i guess you can say it kind of shows an autosomal dominant but at the same time no

if the mother, who is affected, has a male child --> he's going to be affected, but his siblings won't be affected, obviously assuming the woman he marries doesn't have her own mitochondrial DNA defect...😛

 

[step1april2013]

mitochondrial DNA shows variable expression so different people are going to show the severity at different levels...i guess you can say it kind of shows an autosomal dominant but at the same time no

if the mother, who is affected, has a male child --> he's going to be affected, but his siblings won't be affected, obviously assuming the woman he marries doesn't have her own mitochondrial DNA defect...😛

okay good. I'm just making sure because in FA the genogram shows the mother always expresses it, so I wanted to make sure there were no exceptional variations.

 

[Jonari]

what did you choose for that renal picture question in block 1 or 2?

 

[Jamiu22]

very nice thank you

On an unrelated note...In order to classify a disease as having mitochondrial inheritance does the mother have to express the disease (show the phenotype) in order to pass the disease down to her offspring or can the disease be hidden and still be passed down? (I guess what I'm saying is does the mitochondrial inheritance show a kind of autosomal dominant inheritance, where every affected person shows the phenotype)

I agree

Can someone help me with my above question

For Mitochondrial inheritance, I don't see how you can designate it as either dominant or recessive, it's impossible since the gene doesn't occur in pairs like you have nucleic acids. The gene is carried on the mitochondrial DNA, so when gene is passed to the child, they will have the genes for the disease... but if your question is would they show the symptom of the diseases. now that would depend the particular molecule being synthesized for that gene...so what I'm saying is that with mitochondrial inheritance, you could still have incomplete penetrance or variable expressivity.... so although the child inherits the genotype, the phenotypic expression would be different (an example that comes to mind is MELAS)...


This is what comes to mind from my M1 course....it could be completely reasonably wrong.

 

[step1april2013]

what did you choose for that renal picture question in block 1 or 2?

I don't remember that specific question, post it so i can refresh my memory.

For Mitochondrial inheritance, I don't see how you can designate it as either dominant or recessive, it's impossible since the gene doesn't occur in pairs like you have nucleic acids. The gene is carried on the mitochondrial DNA, so when gene is passed to the child, they will have the genes for the disease... but if your question is would they show the symptom of the diseases. now that would depend the particular molecule being synthesized for that gene...so what I'm saying is that with mitochondrial inheritance, you could still have incomplete penetrance or variable expressivity.... so although the child inherits the genotype, the phenotypic expression would be different (an example that comes to mind is MELAS)...


This is what comes to mind from my M1 course....it could be completely reasonably wrong.

True, but for step 1 I believe if they wanted to hint toward incomplete penetrance or variable expressivity they would explicitly say something about it in the question stem. For now, I believe just knowing the stereotypical genogram is good enough. You did help to clear a lot for me with your explanation especially when it is tied with the concept of heteroplasmy

 

[Jonari]

I don't remember that specific question, post it so i can refresh my memory.





True, but for step 1 I believe if they wanted to hint toward incomplete penetrance or variable expressivity they would explicitly say something about it in the question stem. For now, I believe just knowing the stereotypical genogram is good enough. You did help to clear a lot for me with your explanation especially when it is tied with the concept of heteroplasmy

nvm, that was another nbme

 

[Jonari]

For Mitochondrial inheritance, I don't see how you can designate it as either dominant or recessive, it's impossible since the gene doesn't occur in pairs like you have nucleic acids. The gene is carried on the mitochondrial DNA, so when gene is passed to the child, they will have the genes for the disease... but if your question is would they show the symptom of the diseases. now that would depend the particular molecule being synthesized for that gene...so what I'm saying is that with mitochondrial inheritance, you could still have incomplete penetrance or variable expressivity.... so although the child inherits the genotype, the phenotypic expression would be different (an example that comes to mind is MELAS)...


This is what comes to mind from my M1 course....it could be completely reasonably wrong.

i think he was asking is it like a. dominant because of the mere fact multiple people are affected per generation, which is true with mitochondrial diseases - everybody is affected...what you've posted is obviously common sense