[aktorque]

A blood group O, Rh negative woman with a negative antibody screen and no previous administration of Rh immune globulin during her pregnancy delivers a blood group B, Rh positive baby. The baby develops unconjugated hyperbilirubinemia a few hours after birth. The pathogenesis of the baby's jaundice is most closely related to?

A. Maternal anti-D antibodies destroying the babies Rh positive RBCs
B. intravascular hemolysis of fetal RBCs by anti-B IgM antibodies
C. Intravascular hemolysis of fetal RBCs by anti-A,B IgG antibodies
D. extravascular hemolysis of fetal RBCs by anti-B IgG antobodies
E. extravascular hemolysis of fetal RBCs by anti-A,B IgG antibodies

good luck!

 

[usmle0987]

D

D. extravascular hemolysis of fetal RBCs by anti-B IgG antobodies.

 

[donofitaly]

D. extravascular hemolysis of fetal RBCs by anti-B IgG antobodies

 

[khanar]

Explanation!

I think people should mention the reason why they think this or that answer is correct

 

[Mondoshawan]

Are we not choosing A because of the wording that makes it sound like the antibodies are doing the destroying, or is there something in the clinical scenario that makes D more probable? It doesn't say whether it's her first baby...

 

[khanar]

It doesn't say whether it's her first baby...

We should conclude it's the first baby because her antibody screen was negative.

 

[Mondoshawan]

We should conclude it's the first baby because her antibody screen was negative.

Excellent - then I agree with usmle0987 and donofitaly that it's D. Extravascular because they would be destroyed in the spleen, and anti-B because the baby is B (and I'm not sure what E is trying to say, exactly...)

 

[pnreddy]

Excellent - then I agree with usmle0987 and donofitaly that it's D. Extravascular because they would be destroyed in the spleen, and anti-B because the baby is B (and I'm not sure what E is trying to say, exactly...)

yup..i agree with all u guys,,,,and the answer is d..extravascular hemolysis by anti-b antibodies and its igG b'coz its the only antibody transfered transplacentally.....

 

[donofitaly]

I think people should mention the reason why they think this or that answer is correct

1) ABO incompatibility is the only thing that produces unconjugated hyperbilirubinemia within first 24 hours.
2) Physiological Jaundice starts on 2nd or 3rd day.
3) This being her first baby and negative Ab screen, anti Rh Ab is not the factor to be considered.

P.S. Sorry, i will try and give my explanation next time onwards. Its just that i do the questions here in the morning before going to UW hence i don't have much time to type in (mainly because i am lazy).

 

[usmle0987]

Sorry..!!

I think people should mention the reason why they think this or that answer is correct

was about to signout just wanted to answer the question.
exp: assume thats the first child, negative Ab screen, anti Rh Ab can not be considered.extravasular hemolysis causes unconjugated hyperbilirubinemia.

 

[drahmednawaz]

Wana more on my blood!! here come two more Qs

1. Natural antibodies to ABO antigens are usually of IgM isotype, do not cross the placenta, and do not cause problems if the fetus expresses a paternal ABO antigen lacking in the mother. However, ABO antigens sometimes give rise to an IgG response. In which situation would there be the highest probability of production of anti-ABO IgG that could produce erythroblastosis fetalis?

Mother's Blood Type Father's Blood Type
A. AB O
B. O AB
C. A A
D. O O
E. O O Bombay

2. Tests were done to determine a patient's blood type. Results are shown below.
[Controls indicated that all reagents and assays worked properly.]

Test reaction result
Patient erythrocytes + anti-A serum No Agglutination
Patient erythrocytes + anti-B serum Agglutination
Patient erythrocytes + anti-Rh(D) serum No Agglutination

Patient serum + Type A erythrocytes Agglutination
Patient serum + Type B erythrocytes No agglutination
Patient serum + Type O erythrocytes No agglutination

What is the patient's blood type?
A. A, Rh positive
B. A, Rh negative
C. B, Rh positive
D. B, Rh negative
E. AB, Rh negative

 

[rsin21]

1: B
2: D

 

[pnreddy]

the ans to this one is b..mothers being o(having anti-a and anti-b in plasma)and fathers being AB....The baby born is likely 2 be either A or B blood group
and the answer to the second ques is b negative..d
please correct me if i am wrong...

 

[drahmednawaz]

rsin21 and pnreddy, you both are right. It seems that everybody is getting expert in blood antigens.

There is a point i wanted to bring out in the second Q. To determine blood type, we normally treat patient's erythros with with anti-A, anti-B or anti-Rh serum. But they may give u the opposite. Treating a patient's serum with type A, B, or Rh erythro's. They may give u both reactions or either one of them.

 

[aktorque]

Let me answer your qn first,

1. Natural antibodies to ABO antigens are usually of IgM isotype, do not cross the placenta, and do not cause problems if the fetus expresses a paternal ABO antigen lacking in the mother. However, ABO antigens sometimes give rise to an IgG response. In which situation would there be the highest probability of production of anti-ABO IgG that could produce erythroblastosis fetalis?

Mother's Blood Type Father's Blood Type
A. AB O
B. O AB
C. A A
D. O O
E. O O Bombay

2. Tests were done to determine a patient's blood type. Results are shown below.
[Controls indicated that all reagents and assays worked properly.]

Test reaction result
Patient erythrocytes + anti-A serum No Agglutination
Patient erythrocytes + anti-B serum Agglutination
Patient erythrocytes + anti-Rh(D) serum No Agglutination

Patient serum + Type A erythrocytes Agglutination
Patient serum + Type B erythrocytes No agglutination
Patient serum + Type O erythrocytes No agglutination

What is the patient's blood type?
A. A, Rh positive
B. A, Rh negative
C. B, Rh positive
D. B, Rh negative
E. AB, Rh negative

the ans to this one is b..mothers being o(having anti-a and anti-b in plasma)and fathers being AB....The baby born is likely 2 be either A or B blood group
and the answer to the second ques is b negative..d
please correct me if i am wrong...

@pnreddy - you are correct.

Qn # 1 ans is B) Mother O type and Father AB type - when a mother of genotype OO (blood group O) carries a fetus of genotype AO (blood group A) or genotype BO (blood group B), she may produce IgG anti-A and IgG anti-B antibodies respectively. The father will either have blood group A, with genotype AA or AO, or more rarely, have blood group AB, with genotype AB.

Qn # 2 ans is D) B, Rh negative - The qn above mentioned that they have tried different type of blood test to see if the pts blood agglutinating or not, from the test results have given above, we can come to the conclusion that the pt RBC doest not produce clumping to drop of anti-A, anti-B and anti-Rh serum but his RBC only produce clumping to drop of anti-B serum into pts blood sample.

 

[aktorque]

E) extravascular hemolysis of fetal RBCs by anti-A,B IgG antibodies

Ans to my qn is E) extravascular hemolysis of fetal RBCs by anti-A,B IgG antibodies

The mother is ABO and Rh incompatibility with her baby. She has not been previously sensitized to D antigen, so it can not explain the baby's jaundice, therefore, ABO hemolytic disease of the new born is the most likely cause.

In ABO hemolytic disease of the newborn maternal IgG antibodies with specificity for the ABO blood group system pass through the placenta to the fetal circulation where they can cause hemolysis of fetal red blood cells which can lead to fetal anemia and hemolytic disease of the newborn. In contrast to Rh disease, about half of the cases of ABO hemolytic disease of the newborn occur in a firstborn baby and ABO hemolytic disease of the newborn does not become more severe after further pregnancies.

The ABO blood group system is the best known surface antigen system, expressed on a wide variety of human cells. For Caucasian populations about one fifth of all pregnancies have ABO incompatibility between the fetus and the mother, but only a tiny minority develop symptomatic ABO hemolytic disease of the newborn. The latter only occurs in mothers of blood group O because they can produce enough IgG antibodies to cause hemolysis.
Although very uncommon, cases of ABO hemolytic disease of the newborn have been reported in infants born to mothers with blood groups A and B.

Ref:
http://legacy.owensboro.kctcs.edu/gcaplan/anat2/notes/Notes6 Blood Cells.htm

 

[Mondoshawan]

Why E instead of D?

 

[aktorque]

Why E instead of D?

B/c we can not say that anti-B IgG antibody is the one hemolyzing the fetus RBCs. It can be either anti-A or anti-B IgG antibodies causing hemolysis of fetal red blood cells.

 

[donofitaly]

B/c we can not say that anti-B IgG antibody is the one hemolyzing the fetus RBCs. It can be either anti-A or anti-B IgG antibodies causing hemolysis of fetal red blood cells.

How can it be anti-A when there is no A Ag present in fetal blood???

 

[aktorque]

How can it be anti-A when there is no A Ag present in fetal blood???

Fetal RBC surface A and B antigens are not fully developed during gestation and so there are a smaller number of antigenic sites on fetal RBCs. IgG anti-B (or IgG anti-A) antibodies that enter the fetal circulation from the mother find B (or A) antigens on many undifferentiated fetal cell types and started to destroy them.