Lecture 7: Cystic Fibrosis/Familial Aortic Anneurysm/Hypercholestemia Flashcards
Cystic Fibrosis (3)
- most frequent, life-limiting, autosomal recessive* d/o in caucasian population
- incidence: 1 in 2,000 -3,500
- frequency of carriers in US is 1:25
Pulmonary Symptoms of CF (3)
- result from obstruction of tubular structures by viscous secretions
- sx begin in first year of life (classic type)
- respiratory symptoms most prominent features
- chronic cough due to airway resistance
- recurrent pneumonia
- nasal polyps
- nose bleeds
- chronic sinusitis (ex. resistance to first line abx)
- structural changes in airway: cysts, abscesses, fibrosis
- hemoptysis (coughing up blood) in acute infection -> iron deficiency anemia
* occur in first few months of life - commonly isolated pathogens
- s. aureus
- pseudomonas aeruginosa
Pancreatic and GI symptoms (6)
- complications from exocrine pancreatic insufficiency are other major clinical components of classic CF
- prod. abnormal secretions result in obstruction and dilation of pancreatic ducts -> fibrosis and formation of cysts
- affected children show bulky, fatty, and malodorous stools (steatorrhea)
- develop significant failure to thrive and hypoproteinemia - long term symptoms: deficiency of fat soluble vitamins, A, D, E, K
- diabetes melitis
- male infertility (azoospermia): congenital absence of vas deferens
Genetics CF (6)
- caused by mutation on CFTR gene on chromosome 7q31.2
- CF transmembrane conductance regulator is an adenosine triphosphate (ATP) dependent chloride channel
- located in apical membrane of epithelial cells - CFTR gene codes for membrane protein that regulates chloride channels in epithelial cells
- autosomal recessive
- delegations, non-sense mutations, frameshift mutations, and splice site mutations of the CFTR gene result in the complete absence of functional CFTR
- more than 1,000 mutations in CFTR gene have been reported
Most frequent mutation in CF (4)
- Delta-F508
- loss of 3 nucleotides CTT causes the final gene production to have a deletion of the amino acid phenylalanine (f) at position 508 of CFTR protein
- altered CFTR protein is processed intracellularly and disintegrates in the cell’s proteasome complex
- majority (60%) caucasian patients with classic CF are homozygous for the mutation p.f508del.
Pathophysiology CT: respiratory
- viscous mucous in the small respiratory pathway
- disrupts mucociliary clearance
- favors bacterial growth
- recurring infections of the respiratory tract
Pathophysiology CT: Pancreas
- secretion that is deficient in chloride, bicarbonate, and water
- blocks pancreatic ducts
- significantly decreased the solubility of secretory proteins (enzymes)
Pathophysiology CT: sweat
- disrupted reabsorption of sodium chloride leads to abnormal composition of sweat
- abnormally salty: diagnostics significance
Diagnosis CT (3)
- may be established in individuals with at lease one phenotypic feature and a mutation in CFTR as evidences by one of the following
a. presence of TWO mutations in the CFTR gene
b. TWO abnormal quantitative sweat chloride tests
- by the quantitative pilocarpine iontophoresis method
c. TWO trans epithelial nasal potential difference measurements
Management/Tx/Surveillance CF (10)
- replacement of pancreatic enzymes and deficient vitamins
- dietary supplement - bronchodilators
- ABX
- mucous thinning agents
- pain management
- anti-inflammatory agents
- respiratory therapy
- lung transplant
- chest physiotherapy
- immunizations
Aneurysm
abnormal, localized dilation of an artery
Aortic Dissection
life threatening condition in which blood from the vessel lumen passes through a tear in the intima into the medial later and spreads along after
Three Layers Aortia
- intima (inner)
- media
- Aventia (outer)
Acute Aneurysm Dissection
- caused by CT defects that result in a loss of smooth muscle fibers and elasticity, thereby weakening the aorta and other arteries
Familial thoracic aortic aneurysm (2)
- presents at an earlier age than sporadic thoracic aneurysm
- diagnosis based on the presence of dilation and/or dissection of the thoracic aorta and a positive family hx that is not attributable to marfan syndrome or other CT tissue abnormalities
Aortic Aneurysm (5)
- most asymptomatic
- pt. may be aware of pulsatile mass
- symptoms related to compression of neighboring structures by an expanding aneurysm
- first suspected when dilation of a vessel is observed on chest or abdominal radiographs
- wall is calcified - may also be discovered by careful palpation during physical exam
Complications of thoracic aneurysm
may compress the
- trachea
- mainstem bronchus
- resulting in a cough, dyspnea, pneumonia
Aortic Dissection Overview (2)
- thought to arise from a circumferential or transverse tear in the intima layer of the vessel wall that allows blood from the lumen
- 2 types
- Type A
- Type B
Type A Aortic Dissection (2)
- proximal
2. ascending aorta involved regardless of site of primary tear
Type B Aortic Dissection (2)
- distal
2. does not involve ascending aorta or arch, confined to descending thoracic and abdominal aorta
Diagnosis Aortic Dissection
- based on presents of dilation and/or dissection of thoracic aorta and a positive family hx that is not attributable to marfan syndrome or other CT abnormality
Major Dx criteria for type A Aortic Dissection (2)
- presence of dilation and/or dissection of ascending thoracic aorta
- diessection of the descending aorta distal to the subclavian after
- can be either/or or both
Aortic Dissection Bundle Questions (3)
- Does the pt. family have a hx of aortic dissection?
- does the pt have marfan syndrome? family hx of marfan syndrome?
- do physical findings suggest the patient may have undiagnosed margin syndrome?
Genetic Testing for Aortic dissection (2, 4 genes to test)
- Autosomal dominant pattern of inheritance
- molecular genetic testing for
- TGFBR2 (2.5%)
- TGFBR1 (1%)
- MTH 11 (1%)
- ACTA2 (10-15%)
Liver Regulation of cholesterol (3)
- synthesis
- removal
- bile salts for elimination - synthesis of lipoproteins
- transport
- triaglycerol, phospholipids, cholesterol, apolipoproteins
Physiology of Plasma Lipids (3)
- lipoprotein refers to lipids, phospholipids, cholesterol, and triglycerides bound to carrier protines
- Lipids (particularly cholesterol) are required by mast cells for the manufacture and repair of plasma membranes for bile acids and steroid synthesis
- dietary and endogenous - strong like between lipoproteins and coronary artery disease
Cycle of Lipid Metabolism (3)
- Dietary fat packaged into chylomicrons for absorption in the small intestine *
- primarily contains triglycerides
- may be removed and either stored by adipose tissue or used by muscle as an energy source - remnant contains cholesterol, which is taken up by the liver
Chylomicrons
function by transporting exogenous lipids from the intestine of the liver and peripheral cells
VLDL
Very low-density lipoprotein
mainly triglycerides plus a carrier protein
LDL
Mainly cholesterol plus a carrier protein
-responsible for delivery of cholesterol to the tissues
HDL
Mainly phospholipids plus a carrier protein
- responsible for reverse cholesterol transports
- returns excess cholesterol from tissues to the liver
- –eliminated as bile or converted to cholesterol-containing steroids
- —can remove excess cholesterol form aterial walls
LCAT
Lectin-cholesterol actyltransferase
-enzyem helps attach free cholesterol HDL, VLDL, LDL
Lipoprotein metabolism occurs in 2 interconnected cycles
- LPL: lipoprotein lipase
2. Lectithin
Lipoprotein Lipase
releases free FA and glycerol from chylomicrons and VLDL into tissues
Lecithin
cholesterol acyl transferase (LCAT) forms cholesteryl esters from free cholesterol and fatty acids
Hypercholesterolemia
High levels cholesterol in blood
Atherosclerosis
CV disease in which lipids and inflammatory cells accumulate in plaques within the walls of the blood vessles
familial Hypercholesterolemia
Arises from a defect in LDL receptors
Familial Hypercholesterolemia (FH) (4)
- important cause of recurrent myocardial infarction and other CV d/o within a family
- autosomal dominant disease
- caused by heterozygous mutation sin the LDL receptor gene (LDLR) - mutations in LDLR are genetic basis for FH
- heterozygous frequency is 1:500
- one of the most common inherited d/o in lipid metabolism
Homozygous LDLR deficiency
- mutation in both alleles LDLR (LDL receptor gene)
- rare
- causes childhood-onset CV disease
Genetic Basis FH
mutations in LDLR (LDL receptor gene)
Genetics FH (5)
- LDL receptor is encoded in LDLR gene
- LDLR binds to LDL particles that function as carriers for cholesterol in the blood
- cell surface receptors for LDL are defective or absent, resulting in unregulated synthesis of LDL-C
- excess cholesterol accumulates in the body and is deposited in tissues in abnormal amounts
- skin, tendons, arteries commonly affected
Founder Effect FH (3)
- occurs in higher frequencies in persons of
- South African
- French Canadian
- Lebanese
- Finnish - provided only a few parent colonizers, allowing mutation to proliferate
- affect results in accumulation of random genetic changes in an isolated population
- founders
Diagnosis FH (4)
- should be suspected in every individual with LDL concentrations above 300 mg/dL
- in combination with elevated VLDL + normal triglycerides + and low HDL - LDL concentrations greater than 600 mg/dL may indicate homozygous* LDLR deficiency
- detailed family hx and lipid studies in relatives are or particular importance
- mutation analysis of LDLR gene is also useful for diagnostic testing within the family
Management and Surveillance FH (3)
- target goal for LDL-C is less than 100 mg/dL
- pharmacotherapy is beneficial in FH heterozygotes with either lipid-lowering stating or statin/bile resin combos
- reduction of LDL-C in adults is directly proportional to a reduction of coronary events
