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A 16 year old female comes to your clinic with a 1 week history of pleuritic chest pain, cough, fever, and purulent sputum. Her history is remarkable for recurrent upper respiratory infections with Streptococcus pneumoniae and Hemophilus influenza five to six times per year since she was 9 months old. Which of the following is most likely the source of her inadequate immune system?
A - Macrophages
B - B lymphocytes
C - T lymphocytes
D - IgE
E - Natural Killer cells
 

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Wow, I had to search for this one quite a bit.

Your answer choice would be B. This patient has Hyper-IgM Syndrome, where a defect in CD40 ligand for CD4 T helper cells that leads to inability to class switch. It presents early in life with severe pyogenic infections. There's high levels of IgM, and very low levels of IgG, IgA, and IgE.

I'm still in a little bit of a doubt with this one though. So if anybody else has other input, I will appreciate it very much.
 

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Wow, I had to search for this one quite a bit.

Your answer choice would be B. This patient has Hyper-IgM Syndrome, where a defect in CD40 ligand for CD4 T helper cells that leads to inability to class switch. It presents early in life with severe pyogenic infections. There's high levels of IgM, and very low levels of IgG, IgA, and IgE.

I'm still in a little bit of a doubt with this one though. So if anybody else has other input, I will appreciate it very much.
This would be a case of "X-linked Hyper-IgM Syndrome". Mutation of the CD40LG gene which codes for the CD40 ligand on T-cells is responsible for this disease, leading to a defect in isotype switching in B cells in secondary lymphoid systems. Therefore, I would select T lymphocytes, C, because the primary defect is on T cells.

I appreciate any further comments.
 

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A 16 year old female comes to your clinic with a 1 week history of pleuritic chest pain, cough, fever, and purulent sputum. Her history is remarkable for recurrent upper respiratory infections with Streptococcus pneumoniae and Hemophilus influenza five to six times per year since she was 9 months old. Which of the following is most likely the source of her inadequate immune system?
A - Macrophages
B - B lymphocytes
C - T lymphocytes
D - IgE
E - Natural Killer cells
I think is B (Strep & HI only...)
 

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I think Bruton's is X-linked making it more or less a boy's disease. Hyper-IgM as far as I know has a number of different forms but the most common is X-linked.

S. pneumoniae and H. influenzae are both encapsulated bacteria (I think) so I am predominantly thinking about defects in immunity that will prevent these from being destroyed. In this case it's probably either deficiency in antibodies or asplenia. So I am guessing probably B cell defects.
 

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Well since this post is from 2010, I doubt we will get a definitive answer but here is my take.

All we are really given is the fact that this girl has had recurrent bacterial infections with two encapsulated organisms. Both of these bacteria are extracellular so they are normally cleared by humoral immunity.

Most causes of Humoral immunity are due to B-cell defects except for Hyper-IgM which is caused by defective CD40L on T-cells. We are not given enough information to distinguish between the different types of humoral immunity so I would vote for a B-cell defect.

Differential Diagnosis includes: Selective IgA deficiency (most common immune deficiency), Hyper-IgM, CVID, and Broton's (not likely because its a female)

Since selective IgA deficiency is the most common and it can present with recurrent URI's, I'd go with B
 
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