CYSTIC FIBROSIS Flashcards
What is the carrier rate of cystic fibrosis?
1 in 25
What is the incidence of live births with cystic fibrosis?
1 in 2500
On what chromosome is the affected cystic fibrosis gene found?
Chromosome 7
What is the name of the protein that is affected in cystic fibrosis?
Cystic fibrosis transmembrane regulator (CFTR)
What is the result of the mutation of the gene encoding the CFTR protein in cystic fibrosis?
Defective c-AMP dependent chloride channel across epithelial cells. This leads to increased viscosity of secretions
Which organs are most affected by cystic fibrosis?
Respiratory system - recurrent chest infections
Exocrine pancreas - insufficiency
What is the most useful test for diagnosing cystic fibrosis?
Sweat test using pilocarpine iontophoresis to induce sweating and then show abnormal quantities of chloride ions in the sweat.
Infection by which organisms does cystic fibrosis predispose the patient to?
S. aureus
H. influenzae
Pseudomonas
What are the long term complications of repeated infections in a cystic fibrosis patient?
Bronchiectasis
Abscess formation
What are the features of cystic fibrosis?
Chest hyperinflation
Crackles
Wheeze
Finger clubbing
Malabsorption and failure to thrive
Steatorrhea
10-20% present in neonatal period with meconium ileus.
What are the features of meconium ileus?
Failure to pass meconium
Bilious vomiting
Distension of the abdomen
Caused by thickened meconium which is secondary to cystic fibrosis
How is cystic fibrosis usually diagnosed?
Screening is part of newborn blood spot using immunoreactive trypsinogen (Guthrie test).
Gold standard diagnostic test is the sweat test - failure of the normal reabsorption of sodium and chloride leads to abnormally salty sweat. Two sweat tests showing a chloride of >60 mmol/L confirms CF.
Genetic testing of most common mutations will also help diagnosis.
What are the non-pulmonary aspects of cystic fibrosis?
Airway - nasal polyps
GI - Distal ileal obstruction syndrome
Pancreas/endocrine - Diabetes, poor growth, osteoporosis
Reproductive - infertility in males due to absent vas deferens
Joints - arthropathy
Vascular - vasculitis
Hepatic - portal hypertension
How are patients with cystic fibrosis managed with regard to the respiratory system?
MDT
Physiotherapy - chest percussion with postural drainage, breathing exercises, positive expiratory pressure masks.
Many centres recommend continuous flucloxacillin therapy in first 2 years of life.
Use of in-dwelling vascular devices (Port-A-Cath) aid regular intravenous antibiotic courses.
Mucolytics such as nebulised hypotonic saline can help mucous clearance
How are patients with cystic fibrosis managed with regard to nutrition?
MDT
High calorie diet
Vitamin supplements (especially fat soluble vitamins)
Pancreatic enzyme supplementation using enteric-coated microspheres which contain amylase, lipase and protease.
