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  #1  
Old 05-11-2014
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Default Immune q

A 35-year-old woman with a bicuspid aortic
valve comes to the physician because of a 1-
week history of a swollen, painful left knee. She
has had occasional fever and progressive fatigue
during the past 4 months. Her temperature is
38.2C (100.8F). Physical examination shows a
tender left knee with an effusion. A grade 2/6
systolic murmur is heard. Echocardiography
shows a vegetation on the aortic valve. Analysis
of synovial fluid aspirated from the left knee
shows many segmented neutrophils; a Gram
stain shows no organisms, and culture is
negative. Microscopic examination of the urine
shows RBCs and RBC casts, but culture of the
urine grows no organisms. Four blood cultures
grow an α-hemolytic streptococcus. Which of the
following is the most likely cause of the joint
and renal disease?
(A) Autoimmune response triggered by a
bacterial antigen
(B) Deposition of antigen-antibody
complexes
(C) IgA nephropathy
(D) Neutrophil response to replicating
bacteria
(E) Type IV (delayed) hypersensitivity to a
bacterial antigen
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  #2  
Old 05-11-2014
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c .. coz alpha hemo is either strep pneumo or strep viridans..

both coz sub acute endo.

def of igA nephro wud cause severe infections with these bact and even nephritic syn as confirmed by rbc cast in urine...

the only question i hv is her knee aspiration showing neutrophils but no bact... which makes me lean a bit towards type hypersensitivity or grp a beta hemo infection.

but as u said its alpha im going with c...

B cud also b d answer
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  #3  
Old 05-12-2014
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E

I think this patient has infective endocarditis
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  #4  
Old 05-12-2014
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Infective Endocarditis---> B
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  #5  
Old 05-12-2014
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Thank you for your reply. I only have the answer which is B but I am sorry that I donnot have explanations. I think this pt is infected with viridans strep. He has subacute bacterial endocarditis considering his previous bicuspid aortic valve and the disease progression. But I still don't know why the answer is B.
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  #6  
Old 05-12-2014
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Quote:
Originally Posted by Redmoon View Post
Infective Endocarditis---> B
You are right. Can you please explain why bacterial endocarditis induced renal and joint disease is type III hypersensitive reaction?
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  #7  
Old 05-12-2014
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B

Type 3 Hypersensitivity shows systemic problems... in this case with renal disease and joint problems.
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  #8  
Old 05-12-2014
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Quote:
Originally Posted by Curacao View Post
B

Type 3 Hypersensitivity shows systemic problems... in this case with renal disease and joint problems.
I agree to that.
__________________
In USMLE, Any fool can know. The point is to understand.
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  #9  
Old 05-12-2014
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Circulatory immune complex induced GN, vasculitis(oslernodes, janeway lesions, roth spots), arthritis(asymmetric) commonly seen in Subacute Endocarditis.
Hence B seems proper answer.
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Old 05-12-2014
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Quote:
Originally Posted by Redmoon View Post
Circulatory immune complex induced GN, vasculitis(oslernodes, janeway lesions, roth spots), arthritis(asymmetric) commonly seen in Subacute Endocarditis.
Hence B seems proper answer.
So ur saying its posy strep gn due strep pneumo or viridans streptococcus.
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  #11  
Old 05-12-2014
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I thought possible SLE before i saw blood culture result. My understanding is she could have SLE which results in joint and renal problems as mentioned in the case. Also she has strep viridans which results in subacute endocarditis.( Maybe SLE caused an immune deficient state). I know it is weird but it is what i understood
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  #12  
Old 05-12-2014
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The answer lies in that fact that Strep Viridans causes Infective endocarditis or even SBE (subacute bacterial endocarditis) and this is one of the manifestations (among the many):

Infective endocarditis can produce both right and left sided valvular lesions:

Left sided lesions tend to embolize to the CNS, Kindeys and Spleen. In addition, diffuse glomerulonephritis can results due to immune complex deposition. Left sided lesions are also associated with retinal and cutaneous emboli.

Right sided lesions on the other hand produce septic pulmonary emboli that cause infarction, emphysema, or pneumonia.


Regarding why we get immune complex deposition, SBE is associated with most cutaneous manifestations (janeway lesions, subcutaneous nodules etc.) and the renal manifestations include flank pain and hematuria.
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  #13  
Old 05-13-2014
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Quote:
Originally Posted by placebo View Post
So ur saying its posy strep gn due strep pneumo or viridans streptococcus.
IMO damaged valve(bicuspid aortic valve ) predisposes to IE/SAE by S. Viridans.Clinical picture in this particular scenario--> Biscuspid valve, vegitations on valve,fever indicates Endocarditis, & asymmetric joint pains with renal involvement indicates IC related damage.
Synovial joint fluid analysis shows --> sterile--> IC deposition,same with Renal finidngs.
I don't see any clue to think of either SLE or PSGN thing.
I have not done Microbiology yet but this is what i remember from rote memory.
My two cents.
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  #14  
Old 05-15-2014
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Post streptococcus glomerulonephritis results from antigenic mimicry from group A strep infections. This is a general type III hypersensitivity reaction. The bacteria on the heart (sub acute bacterial endocarditis from strep viridans seeding a damaged heart valve) are being constantly attacked by the immune system and are in the bloodstream (positive blood cultures). No molecular mimicry is needed to generate immune complexes, as bacterial antigen is in the blood already. It gets complexed and precipitates in the kidney and joints, triggering local, non-specific inflammation.
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