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 marfan's syndrome  



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Author18 Posts
  #1

What is the genetic defect ?




  #2

Fibrillin gene :?:


  #3

can you tell me more about its genetics ?


  #4

Autosomal dominant


  #5

Its associated with chromosome 15q and can exhibit variable expressivity


  #6

thanks


  #7

Description:
Marfan's Syndrome is an inherited (autosomal dominant) disorder, caused by a defective gene involved with the production of fibrillin. Fibrillin makes up part of connective tissue in the body, such as the blood vessels, eye lenses, and ligaments.

Symptoms:
Patient has long, thin arms, legs, fingers, and toes.
Chest wall protrudes
Reduced vision and severe near-sightedness
Mitral valve prolapse

Diagnosis:
Aortic aneurysms (a bulge in the wall or the aorta, resembling a weak spot that bulges in an imperfect automobile tire) -- can have no symptoms; or might have fatigue, lightheadedness, and/or chest pain. Death may occur if the aneurysm ruptures.

Aortic Dissection (a torn area between the layers of the aortic wall, allowing blood to seep between the layers of the wall) -- can cause chest pain, tearing/ripping back pain, or death

Aortic Regurgitation -- chest pain, shortness of breath

Spontaneous Pneumothorax -- Collapsed Lungs may occur (severe, sudden shortness of breath)


Mutations may be seen in chromosome 15, but no single test establishes the diagnosis.
Echocardiogram is performed to evaluate the patient's chest for an aortic aneurysm.
See section on Aortic Dissection for work up and management.
Ophthalmologic evaluation reveals lens dislocation and severe near-sightedness.


  #8

Hi new member.
Please tell me the difference between Marfan's syndrome and Danlos-Ehler's syndrome?


  #9

They have mutations in different proteins:

MF: fibrillin
ED: collagen, usually type 4 (in basement membrane)


  #10

what is the difference betn EHLARS DANLOS & OSTEOGENESIS IMPERFECTA??


  #11

ehler danlos....type 4 collagen disease
osteogenesis imperfecta..........type 1 collagen disease .


  #12

Type I is distributed in Bones and vessels, so that's why "easy fructure"
Type IV in basement membrane---> "loose skin"


  #13

good point :idea:


  #14

During wound healing the change of collagen is type 4 to 1 right??


  #15

it's collagen type 3 what u find in first stages of wound repair. (type 4 is in basement mb). so it is 3 to 1. (Cu, Zn, collagenases.......)


  #16

Ok thanks.


  #17

"mjl1717" wrote:
Its associated with chromosome 15q and can exhibit variable expressivity


hmm.. variable expressivity is not characteristic of marfan's :!:

pleiotropy is what characterizes this syndrome (where many organs are affected like cystic fibrosis, a1 antithrypsin def. etc)

variable expressivity is when the phenotype and the symptoms differ from person to person.In Marfan's all persons are tall ,all have spider fingers,all have skeletal deformities... :roll:


  #18

OK Mars-you may have a point.
Ill give some cold definitions that may appear unambiguous to most.

1)Pleiotropy-literally means"many turnings" -a given phenotype is carefully observed at different levels or as you said a mutation that affects multiple organs.

2)Penetrance versing Expressivity (According to Harrisons thses terms are subject of confusion and slight variation in usage

a)Penetrance is the proportion of individuals with a given genotype who present with any phenotypic features of the disorder(usually an all or none
phenomenon)

b)Expressivity or variable clinical expression describes the range of phenotypic effects in individuals carrying a given mutation. This variability
can include the type and severity of symptoms and age of onset of symptoms. Variable in clinical expression is ilustrated dramatically in MEN Type I(The resulting manifestations can be extremely diverse)****In a counseling context, variation in expression, as distinct from penetrance, is the point in question when an individual with a dominant disorder wishes to know whether an offspring who carries the mutaion would have mild or severe symptoms. In molecular terms, analysis of the single gene locus will NOT answer this question(i.e. predict variation in expression within a family) but can determine whether a mutant gene exists.

3)Genetic heterogeneity-Multiple genetic causes of the same, or nearly the same, phenotype.(Hemophilia A and B)

*Marfan facts-1:10,000---once againA.D.---at least one fourth of pts do NOT have an affected parent, and their cases are probably due to new mutations.


Most of this info from Harrisons and Basic Human Genetics by Mange& Mange :idea:





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