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  #1  
Old 11-03-2012
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Immunology Fetomaternal Immunity

A newborn child is exposed to Streptococcus agalactiae and subsequently develops meningitis. Which of the following could have contributed to this child's bacterial infection?


A) A defect in DNA repair enzymes with associated IgA deficiency
B) An X-linked recessive defect in a tyrosine kinase gene
C) Improper development of the thymus and parathyroid glands
D) Improper transfer of IgG from the mother to the fetus
E) Improper transfer of IgM from the mother to the fetus
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  #2  
Old 11-04-2012
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Default my answer :)

I was thinking A) or B)

I'll go with A A defect in DNA repair enzymes with associated IgA deficiency

bc in Bruton's symptoms usu occur after 6 month of age
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Old 11-04-2012
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Quote:
Originally Posted by Casandra View Post
I was thinking A) or B)

I'll go with A A defect in DNA repair enzymes with associated IgA deficiency

bc in Bruton's symptoms usu occur after 6 month of age
may i know, why D didnt come to your thought here....?

am i missing any logic here?......thanks

Last edited by venky2600; 11-04-2012 at 01:31 AM.
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  #4  
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I go with A....................selective IgA deficiency>sinopulmonary infections>meningitis............
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Originally Posted by venky2600 View Post
may i know, why D didnt come to your thought here....?

am i missing any logic here?......thanks
I'm sorry to say that I've never heard of any disease that is caused by improper transfer of IgG............Though I go with answer A, i'm not fully sure about this................
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Originally Posted by subbi View Post
I'm sorry to say that I've never heard of any disease that is caused by improper transfer of IgG............Though I go with answer A, i'm not fully sure about this................
ya you're right....i just didnt thought of diseases, only went through options as statements given and thought it as answer..........then A must be the right answer IMO..
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A newborn child is exposed to Streptococcus agalactiae and subsequently develops meningitis. Which of the following could have contributed to this child's bacterial infection?


A A defect in DNA repair enzymes with associated IgA deficiency
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  #8  
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Originally Posted by venky2600 View Post
may i know, why D didnt come to your thought here....?

am i missing any logic here?......thanks
do you think that maternal IgG could protect a newborn from agalactiae?
If they did, we wouldn't be giving the antibiotics prior/during the delivery to the women who are S. agalactiae carriers.
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  #9  
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Originally Posted by Casandra View Post
do you think that maternal IgG could protect a newborn from agalactiae?
If they did, we wouldn't be giving the antibiotics prior/during the delivery to the women who are S. agalactiae carriers.
oh really...i never thought in that way....may be i was dumb at this

as usual thanks casandra-----always learn something from your posts.......
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Quote:
Originally Posted by venky2600 View Post
oh really...i never thought in that way....may be i was dumb at this

as usual thanks casandra-----always learn something from your posts.......
you were not being dumb - we discuss issues here. only those who think they're always right and refuse to learn anything new are those who are being dumb

edit: ps. besides we still don't know what is the right answer so...
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  #11  
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Well!........let's see what medical examiner tells us..........eagerly waiting for the answer.
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Quote:
Originally Posted by subbi View Post
Well!........let's see what medical examiner tells us..........eagerly waiting for the answer.
@subbi - I'm equally eagerly waiting for the correct answer in your question: http://www.usmle-forums.com/usmle-st...ology-7-a.html
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Quote:
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@subbi - I'm equally eagerly waiting for the correct answer in your question: http://www.usmle-forums.com/usmle-st...ology-7-a.html
Yes fren, i have posted the answer to that question........you need to clear the concepts for me more.............thanx.
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The correct answer is D. Circulating IgG that is passed from the mother to the newborn through the placenta protects the newborn from many microorganisms for the first 6 months of life. Thus, improper transfer of IgG from the mother to the fetus can leave the newborn susceptible to infections. While IgA is found in breast milk, a neonate will have access only to antenatal antibodies, and IgG is the only antibody isotype that can cross the placenta.

Answer A is incorrect. Ataxia-telangiectasia is caused by a defect in DNA repair enzymes with associated IgA deficiency. This usually presents with cerebellar problems (ataxia) and spider angiomas (telangiectasia). It would not cause a neonate to be immunocompromised, because for the first 6 months of life the infant relies on IgG from the mother.

Answer B is incorrect. An X-linked recessive defect in a tyrosine kinase gene is seen in Bruton's agammaglobulinemia. This is associated with low levels of all classes of immunoglobulins. However, with Bruton's agammaglobulinemia, bacterial infections tend to occur after 6 months of age, when levels of maternal IgG antibody start to decline to levels insufficient to provide host defense.

Answer C is incorrect. Improper development of the thymus and parathyroid glands is seen in thymic aplasia (DiGeorge's syndrome). This leads to recurrent viral and fungal infections due to a T lymphocyte deficiency. It would not have any effect on susceptibility to bacterial infections.

Answer E is incorrect. The only antibody iso-type that can cross the placenta is IgG. Therefore, IgM would not play a role in an infant's immunity until an infant can produce it themselves, at the age of 6 months.
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  #15  
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The correct answer is D. Circulating IgG that is passed from the mother to the newborn through the placenta protects the newborn from many microorganisms for the first 6 months of life. Thus, improper transfer of IgG from the mother to the fetus can leave the newborn susceptible to infections. While IgA is found in breast milk, a neonate will have access only to antenatal antibodies, and IgG is the only antibody isotype that can cross the placenta.


Oh..I didn't see this answer coming
So you mean all those new born who get early infection as neonate because they are not getting proper IgG from mother???
Never read or heard about it so curious.
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Old 11-04-2012
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Hahahaha D came into my mind after seeing that question
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Quote:
Originally Posted by koolkiller88 View Post
The correct answer is D. Circulating IgG that is passed from the mother to the newborn through the placenta protects the newborn from many microorganisms for the first 6 months of life. Thus, improper transfer of IgG from the mother to the fetus can leave the newborn susceptible to infections. While IgA is found in breast milk, a neonate will have access only to antenatal antibodies, and IgG is the only antibody isotype that can cross the placenta.


Oh..I didn't see this answer coming
So you mean all those new born who get early infection as neonate because they are not getting proper IgG from mother???
Never read or heard about it so curious.
me too
im adding this to my wtf questions list
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I tried to read a bit about agaclactiae ...

In one article they said that the CAMP factor of this bug initially thought to bind to the Fc component of IgG and act on it was proved false

In another ,they said IgA prevents it from attaching to the mucosa of vagina and a whole lot of crap ...

After reding another , I decided to forget about the question ... Lol
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can i know source of ur q&a
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Quote:
Originally Posted by alice View Post
I tried to read a bit about agaclactiae ...

In one article they said that the CAMP factor of this bug initially thought to bind to the Fc component of IgG and act on it was proved false

In another ,they said IgA prevents it from attaching to the mucosa of vagina and a whole lot of crap ...

After reding another , I decided to forget about the question ... Lol
hehe i already did forget abt it......though i guessed D as the right answer

i hope such controversial q's wont exist in real one
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Source is First Aid Q&A for the USMLE Step 1
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  #22  
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thank you................
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Little individual factoids are like tiny intellectual enemas for every drop of which u have to stretch as Conrad Fischer said and its painful indeed

For me personally to know strep agalactiae as a cause of neonatal meningitis and sepsis is of more value than that individual factoid
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just an another q doctor

did the question stem say anything about maturity of newborn
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My god................good question and shocked...........hehe
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Old 11-05-2012
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my ans is improper transfer of igm from mother to fetus
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Quote:
Originally Posted by venky2600 View Post
hehe i already did forget abt it......though i guessed D as the right answer

i hope such controversial q's wont exist in real one
@venky - see, the joke is on me I'm only comforted by the fact that everyone else were supporting this answer.
However the official explanation doesn't convince me AT ALL
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Quote:
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my ans is improper transfer of igm from mother to fetus
oooh such a silly mistake made ...how could igm travels from placenta...
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Quote:
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oooh such a silly mistake made ...how could igm travels from placenta...
Happens sometimes fren!!.............lol
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Quote:
Originally Posted by Casandra View Post
@venky - see, the joke is on me I'm only comforted by the fact that everyone else were supporting this answer.
However the official explanation doesn't convince me AT ALL
a newborn lacks alveolar macrophages hence more susceptile to strep.agalactiae
infection & it s an encapsulated bug... so igA has no significant role;
(wikipedia)

a premature neonate is more susceptible to this type of infection due to improper transfer of igG abs. (medscape)

hence igG transfer is the best choice

antiobiotic prophylaxis is given to carriers because of changing serotypes

hope this helps
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Quote:
Originally Posted by Casandra View Post
@venky - see, the joke is on me I'm only comforted by the fact that everyone else were supporting this answer.
However the official explanation doesn't convince me AT ALL
@casandra--ya even i agree with you,the explanation didnt convince me...so according to it, we answer the questions just by looking the options stated even though the kind of disease exist or not(i mean D is not assciated with any diseases we usually see) which is contradictory IMO
but, the options itself are not clear.......i think no other options too gives the appropriate answer.......(with A too ,never heard such association with S.agalactae.....)
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Quote:
Originally Posted by venky2600 View Post
@casandra--ya even i agree with you,the explanation didnt convince me...so according to it, we answer the questions just by looking the options stated even though the kind of disease exist or not(i mean D is not assciated with any diseases we usually see) which is contradictory IMO
but, the options itself are not clear.......i think no other options too gives the appropriate answer.......(with A too ,never heard such association with S.agalactae.....)
So can we conclude that
those neonates who are getting infected are basically because they are not getting IgG from mothers? (except TORCHS)
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Originally Posted by koolkiller88 View Post
So can we conclude that
those neonates who are getting infected are basically because they are not getting IgG from mothers? (except TORCHS)
no dude, we cant conclude.....coz not all the babies getting S.agalactae infection has similar prob.(not getting IgG)......i'm just talking with related to this Q..
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