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 Marfan's  



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Author19 Posts
  #1

Which of the following statements concerning Marfan syndrome is true?

A) Marfan syndrome is an example of genetic heterogeneity.
B) All patients should have a slit-lamp examination.
C) The skin examination is usually unremarkable.
D) Most patients have a mutation in the gene coding for elastase.
E) This disorder is generally inherited as an autosomal recessive disorder

sad





  #2

I will go with C (none of the other is right)



  #3

B?

lens dislocation is a major criterion for diagnosis, and ectopia lentis is present in 50% patients

striae atrophicae and recurrent hernia could be skin involvement..



  #4

emmm...why not A./..marfan's is an example of genetic heterogeneity i thought...both marfan's n homocystinuria have very similar symptoms..so have to differentiate by nitroprusside test...confused

Answer that i got is slit lamp examination...and as An said..ectopia lentis is present in most of marfan's...n it sure is indicated to establish a diagnosis of marfan's..so can't really exclude choice B too..

any other inputs? confused



  #5

prod, u have made a very good point...in fact, there r different fibrillin mutations all giving rise to Marfan syndrome..so (A) has to be right too...


  #6

Slit-lamp examination is needed to detect Kayser-Fleischer ring in cornea in Wilson disease, you don't need it to detect lens dislocation in Marfan syndrome, it is obviuos by even unaided eyes, so A is a correct answer.


  #7

aight...lol p53..i still don't know the correct answer to this question..all i have is an answer from someone in a forum...n that person didn't give me a reference.,..raised eyebrow.

i'll type harrison verbatim grin

Diagnosis

The diagnosis is easily established if the patient and other members of the family have dislocated lenses, aortic dilatation, and long and thin extremities together with kyphoscoliosis or other chest deformities. The diagnosis is frequently made if ectopia lentis and an aneurysm of the ascending aorta occur in the absence of a Marfan habitus or a positive family history. All patients with suspected diagnosis should have a slit-lamp examination and an echocardiogram. Also, homocystinuria should be ruled out by a negative cyanide-nitroprusside test for disulfides in the urine. A few patients with types I, II, and III EDS have ectopia lentis but lack the Marfan habitus and instead have characteristic skin changes not present in MFS. Patients with familial aortic aneurysms tend to develop aneurysms at the base of the abdominal aorta. The location of the aneurysms, however, is somewhat variable, and the high incidence of aortic aneurysms in the general population (1 in 100) makes the differential diagnosis difficult unless other features of MFS are clearly present. A few families with familial aortic aneurysms have mutations in the gene for type III procollagen.

Alright...moreover its also written that diagnosis of ectopia lentis requires slit lamp..so..B can't be wrong either....so here you go lol





  #8

OK, I was wrong, then it's B, there couldn't be 2 correct answers.


  #9

The correct answer is B


  #10

rojas..p53,....everyone..i posted this question..cuz i heard that the answer is B...from another forum..n that person never gave me any reference or any logic to why is it not choice A..

I am sorry...but i really don't have the answer as i don't know from which book this question is from sad

Can anyone shed any light



  #11

well according to goljan book "a" is correct answer.


  #12

I guess it is A because:
genetic heterogeneity= manifestation of similar or the same observable characteristics or traits resulting from different genetic mechanisms, such as mutations of different genes or a combination of genes.
Marfan has mutation to cs 3 and 5.



  #13

ok.. so B is correct..
NE I didn't know that marfan's is caused by a defect in 5th and 3rd... doesn't seem right 'cause it's fibrillin and that should be on one cromozome only.. i don't feel like searching for the answer..

marfan's is a typical example of pleiotropy.. didn't know heterogeneity too

also, why isn't C a good answer?


  #14

Marfan causes:
-Principal- mutations in the fibrillin-1 gene located on chromosome 15q21.( sorry for the typing mistake is not cs5)
Other- increased susceptibility of fibrillin to proteolysis ( cs 3)
It is true than ectopia lensis is a major diagnosis criteria in Marfan so slit-lamp examination should be done for diagnosis.
Now I think B is a better choice ( is so good to drink a cup of coffee!!).grin


  #15

yes, but what would a skin exam detect (abnormal)?



  #16

www.nlm.nih.gov/medlineplus...us/ency/article/003880.htm



  #17

A is the right answer.

Marfan can be casued by mutation in FBN1 (dominant negative mechanism) and TGFB2 gene
(loss of function mechanism). it matches exactly the concepts of genetic heterogeneity

genetic heterogeneity= manifestation of similar or the same observable characteristics or traits resulting from different genetic mechanisms, such as mutations of different genes or a combination of genes.


  #18

totally agree with manu nastai!!! nod

i did not know either marfan was in different genes, i knew about pleitropy (in fact it is one of the best known examples of different system due to connective tissue abnormalities)


  #19

i remember this question from some qbank and B was the answer.
Besides u know they always put A as distractors





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