Cystic Fibrosis

Question 1

Definition

Answer 1

Genetic condition characterised by multi system disease notably respiratory tract infections, pancreatic insufficiency, malabsorption and male infertility

Question 2

Mode of inheritance

Answer 2

Autosomal recessive

Question 3

Pathology

Answer 3

Defect of CFTR gene on chromosome 7q.
Encodes chlorine channels which regulate sodium and chlorine in exocrine secretions.
Results in thick viscous secretions.

Question 4

Changes to the lung in CF

Answer 4

mucous gland hyperplasia, recurrent infections leads to fibrosis, consolidation, bronchietesis

Question 5

epidemiology

Answer 5

1 in 2500 live births

Question 6

how common is it to carry the defective gene

Answer 6

1 in 25

Question 7

history

Answer 7

Lung - recurrent infections, chronic cough, wheeze, sputum, haemoptysis
Gut - meconium ileus in neontes, steatorrhea
Other - chronic sinusitis, nasal polyps, male infertility, arthritis

Question 8

examination

Answer 8

chest wall deformities, coarse creps, wheeze, anaemia, weight loss, vitmin deficiencies, slow growth, failure to thrive, delayed puberty, clubbin, nasal polyps, signs of diabetes, hepatomegaly

Question 9

Investigations

Answer 9

Sweat test - pilocarpine (muscarinic agonist) iontophoresis (low electircal current) stimulates sweating which is collected and analysed (increased >60mmol of chlorine is diagnostic)

Neonatal screeing with day 6 guthru heal prick is now standard method of diagnosis. blood tested for trypsin (raised 2-5x in CF)

CXR- may be normal, increased bronchial markings, ring shadows, fibrosis, consilidations, bronchiectesis

Pancreas- faecal elastase, faecal fat content, GTT, HBA1c

Genetic analysis rarely necessary

Lung function test to assess function and prognosis

Question 10

Management

Answer 10

MDT and specialist care.

Resp - physio, positive pressure masks, bronchodilators, antibiotics for exacerbations and propylaxis, flu vaccine, nebulised rhDNase and hypertonic saline to reduce secretions and clear mucus

GI - nutrition, oral pancreatic enzyme replaceemnt

Endocrine- treat if diabetes develops

Surgical - end stage disease may merit single lung or heart lung transplant

Question 11

complications

Answer 11

recurrent chest infections
bronchiectesis, malabsoption, rectal prolapse, type 1 diabetes, male infertilty, gallstones, neonatal complications eg meconium ileus and intussusception.

Question 12

prognosis

Answer 12

life expectancy in third decade but improving.

pancreatic insufficiency and pseudomonas colonisation poorer prognosis.

Question 13

most common organisms for infection/colonisation in CF

Answer 13

haemophilus, Staph and pseudomonas