Cystic Fibrosis

Question 1

What is Cystic Fibrosis ?

Answer 1

Inherited condition -Autosomal recessive - need to inherit gene from both parents (if only one inherited - carrier)

Build up of excess sticky mucus in lungs + digestive system.

Mostly effects lung + pancreas
- characterised by lung infections +
problems digesting food.

(cystic - fluid filled sacs
Fibrosis - excess connective tissue deposition)

Question 2

What causes Cystic Fibrosis ?

Answer 2

mutation in CFTR gene - encodes for CFTR protein

(CFTR - Cystic Fibrosis Transmembrane conductance Regulator )

CFTR protein -
0 a pump on the membrane
0 pumps CL- ions into secretions
0 drawing water into secretions - thinning it out.

Mutation is CFTR gene - different types of mutations have different effects (protein can be misfolded , not migrate from endoplasmic R to membrane etc)

• not enough CL- pumped into secretion —-> h20 not drawn —–> secretions too thick.

Question 3

What are the different types of mutations and classes of CF?

Answer 3

Class 1 : No functional CFTR protein created.

Class2 :CFTR created , but misfolded so does not reach surface membrane. 
           []F508 - MOST 
             COMMON - 
             DELETION OF 
             508TH 
             phenylalanine so 
             CFTR becomes 
             misfolded)
(square supposed to be a triangle0

Class 3: CFTR created, reaches surface membrane but does not function correctly.

Class 4 : opening of ion channel of protein is faulty
(cl- cannot get out)

Class 5 : CFTR produced in insufficient quantities

Question 4

What are the complications of CF?

New-borns
Early childhood

Answer 4

New-borns - Meconium ileus - surgical emergency

meconium (first stool becomes thick and sticky ) ——-> gets stuck in intestine.

Early Childhood -

pancreatic insufficiency - thick mucus/ secretions block pancreatic duct

0 Blocked duct —-> no pancreatic enzymes released into duodenum—-> protein and fat not broken down and not absorbed.

• causes:
  0 poor weight gain
  0 failure to thrive
  0 Steatorrhea (fat containing stools)

Distal intestinal obstruction syndrome - lack of absorption can cause partial or complete bowel blockage

Pancreatic enzymes have nowhere to go so start to digest pancreatic lining causing damage leading to :

Acute pancreatitis - short term
Chronic Pancreatitis - long term

Endocrine dysfunction - pancreatic damage then effects endocrine function - release of hormones e.g. insulin.
0 lack of insulin - development of insulin dependent diabetes.

Question 5

What is Distal intestinal obstruction syndrome ?

Answer 5

complication of CF

Fat not digested - stool thickens causing blockage - partial or complete

usually occurs at the junction btw distal ileum and right colon (where small nowel joins large bowel)