Cystic Fibrosis Flashcards
What is Cystic Fibrosis?
Cystic Fibrosis is an autosomal recessive diseased characterized by a defective Chlorine (Cl-) channel with-in the cell membrane of the respiratory system. The defect leads to hypersecretion of fluid in the gastrointestinal tract, respiratory tract, and the respiratory system.
What gene and chromosome is affected in Cystic Fibrosis?
The CFTR gene of Chromosome 7.
What is the CFTR gene?
Cystic Fibrosis Transmembrane Regulator Gene
What type of glands are responsible for secreation of fluids? They are also the glands affected by Cystic Fibrosis.
Exocrine Glands
What is the pathophysiology of Cystic Fibrosis?
Cystic Fibrosis Transmembrane Regulator Genes normally form Chloride (Cl-) channels on epitheal cells. However, due to mutations of the CFTR gene, cells are impermeable to Cl-. Impaired Cl- transport across the cell membrane results in abnormal secretion. A thick mucus forms, known as a mucus blanket, which conversly decreases ciliar function and plugs airways decreasing the function of the lungs. The excessive secreations also are ideal breeding gounds for bacteria, resulting in chronic bacterial infections. Over 90% die with severe pulmonary disease.
Where do the Chloride ions come from? How do they get into the cells?
Cl- ions come for the blood stream. They permeate from the vasculature, into the cells of the respiratory tract.
What is the name of the exocrine cell in the respiratory and intestinal tracts?
Goblet cell
What occurs inside the Goblet cell when the Chloride channels are mutated?
Chloride channels are mutated, inhibiting the normal transport of chloride from the goblet cell into the lumen of the airway. The goblet cell’s cytoplasm becomes concentrated with the excess chloride. Due to the higher concentrations, water will move to the higher concentration in the goblet cell, followed by sodium.
What is the function of a Goblet Cell?
A goblet cell is found in the respiratory and intestinal tracts. It is responsible for secreting the main component of mucus.
What is the effect on mucus when Chloride channels are mutated and chloride is blocked inside the goblet cell in a Cystic Fibrosis patient?
The movement of water and sodium into the goblet cells due to movement towards the concentration gradient caused by the high chloride concentration result in the mucus becoming thick and more difficult to exporate.
What is the resulting effect when mucus become too thick to exporate in a cystic fibrosis patient?
Airway obstruction and bacteria proliferation.
What is the standard test for cystic fibrosis diagnosis?
Sweat test
Exlain what a sweat test is for cystic fibrosis diagnosis?
A sweat test is the standard test which measures the concentration of Na+ and Cl- in perspiration. A patient with cystic fibrosis will have elevated levels of Na+ and Cl- two to five time greater than an normal, healthy individual.
What are several other diagnostics beyond a sweat test for cystic fibrosis?
Newborn Screening, Cystic Fibrosis in a sibling, GI and Repsiratory Manifestations.
When screening for cystic fibrosis in a newborn, what is measured? Why are the levels of this substance elevated in newborns with cystic fibrosis?
Cystic fibrosis in a newborn screening is a process of measuring the level of immunoreactive trypsinogen in the blood of the newborn. Trypsinogen is a pancreatic enzyme which is found in elevated levels in babies with cystic fibrosis because the pancreatic ducts are partically blocked leading to abnormal enzyme drainage. If the infant has elevated trypsinogen level in two consequtive tests, they will be referred for a sweat test.
