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27 Cards in this Set

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How is Cystic Fibrosis inherited?
Autosomal recessive
What is the primary defect in Cystic Fibrosis?
Epithelial Chlorida Channel protein
What gene encodes for it?
Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene on the long arm of chromosome 7.
Functioning CFTR ↓ Na+ channels. mutant CFTR doesn't. What is the sole exception to this?
Human sweat glands.

Mutant CFTR ↓ Na+ with ↓ Na+ into the cell.
How many ATP binding domains does it have?
Two

1) closed channel (Cl-, Na+)

2) regulatory domain (must be phosphorylated)
What are the six classes of CFTR gene mutations?
Class 1: Defective protein synthesis due to defective mRNA
Class 2: Abnormal protein folding, processing & trafficking. Fails to escape ER.
Class 3: Defective regulation and channel
Class 4: ↓ conductance resulting in ↓ Cl- current
Class 5: ↓ CFTR gene ↓ CFTR
Class 6: Altered regulation of seperate ion channels.
Describe the most common mutation in Cystic Fibrosis?
Class II: abnormal proteins don't escape ER to Golgi.

Mutation: 3 base pair deletion Coding: phenylalanine
Position: ΔF508
What does CFTR activate in the pancreas? What is then kept in the cell?
cAMP activated Cl- & HCO3 exchange channel.

HCO3, Na+, H2O, activated digestive enzymes
What is the main symptom of pancreatic cystic fibrosis?
Steatorrhoea secondary to fat malabsorption
What is meconium ileus?
Inability for a newborn to pass their first stool.
What is the most important screening test for cystic fibrosis?
Sweat test
What are the respiratory symptoms of cystic fibrosis?
Chronic cough
Nasal obstruction secondary to chronic sinustitis
Small airway obstruction secondary to persistent lung infection
Bronchiolitis
Respiratory failure
What are the gastrointestinal symptoms of cystic fibrosis?
Pancreas - secondary to maldigestion, lack of digestive enzymes or intestinal obstruction
- Fat & protein maldigestion and absorption
- Steatorrhoea
- Fat soluble vitamin deficiencies
- Recurrent pancreatitis secondary to autodigestion
- Hyperglycemia requiring insulin
Intestine
- Meconium ileus
- Abdominal distension
- Vomiting
What are the genito-urinary symptoms of cystic fibrosis?
Late onset of puberty (male & female)
Azoospermic secondary to vs deferens obliteration (male)
How is cystic fibrosis managed?
Symptomatically
Respiratory
- mucus clearance (breathing exercises, chest percussion)
- human DNAase to break down DNA released by dead neutrophils
- Prophylactic antibiotics vs lung infections
- Bronchodilators (vs acute ep)

Gastro-intestinal
- pancreatic enzyme replacement
- fat soluble vitamin supplements
- high caloric diet, low in fat & high in protein
Where is the mutation causing sickle cell anaemia?
6th position of β-globin chain
What is replaced in the sickle cell mutation?
Glutamic acid (neg) replaced by valine (uncharged)
What are the clinical features of sickle cell anaemia?
- Haemolytic anemia - unable to pass spleen and destroyed.
- Sickling crisis - hypovolemic shock secondary to severe anemia, rapid splenomegaly
- Vaso-occlusive disease/pain crisis - responsible for morbidity and mortality. Secondary to microcirculation obstruction leading to ischaemic injury to abdomen, bones, joints and soft tissue.
- Chronic hyperbilirubinemia - ↑ unconjugated bilirubin secondary to hemolysis. Pre-hepatic jaundice. ↑ chance of gall stone formation.
What three tests are performed for sickle cell anemia?
Electrophoresis - HbS is not as negative due to valine

Allele specific oligoucleotide (ASO) test - gene probe

RFLP analysis
What is the histological sign of X-linked muscular dystrophy?
Muscle fiber replacement by fibrofatty tissue
Where is the mutant gene in X-linked muscular dystrophy?
p21 region of the X chromosome that encodes for dystrophin.
What does dystrophin do?
intracellular protein in myocytes that forms strong mechanical link to actin over z-lines that transfers the force of contraction to CT.
What are the clinical features of Duchenne Muscular Dystrophy (DMD)?
Most common, most severe.
Complete absence of dystrophin from deletions and frame shift mutations.

- present at birth but presents at 3-5
- delayed walking & clumsiness
- weakness beginning in pelvic girdle and moving to shoulder
- learning difficulties
- death by 30 due to respiratory failure of cardiomyopathy
What are the clinical features of Becker Muscular Dystrophy (BMD)?
Mutated dystrophin

- present between 5-15 or as late as 30-50
- same muscle wasting pattern
- death between 40-60
How is X-linked muscular dystrophy diagnosed?
Clinical features
↑ Creatine Kinase (CK)
Characteristic muscle biopsy
Immunohistochemical staining
How do you treat X-linked muscular dystrophy?
Glucocorticoids can slow progression by 3 years
Orthopaedic devices or corrective surgery
Tacheostomy or ventilatory support