Inherited Respiratory System Disorders

Cystic Fibrosis (CF) CF is the most common life-limiting autosomal recessive disorder in white population. CF is chronic, progressive, and frequently fatal genetic disease of the mucous glands. Affects the respiratory and digestive systems in children and young adults. An average person has a lifespan of 40 years with the right treatment.

Cystic Fibrosis Cystic Fibrosis is caused by a defective CFTR gene which codes for a Na+ and Cl- transporter found on the surface of epithelial cells of lungs and other organs. CFTR - Cystic Fibrosis Transmembrane conduction Regulator

Cystic Fibrosis Autosomal recessive Gene cloned in 1989: “CFTR” 1601 mutations in CFTR known to cause CF An extensive amount of information is known about CFTR Science, September 1989

Pathophysiology of CF CFTR Mutation Epithelial cell dysfunction Disease manifestations Lungs Sinuses Pancreas Liver Biliary duct Bones Vas deferens ?

CF Lung Chloride does not get into airway; more sodium leaves; mucus is thick

Airway Cross Sectional View Knowles & Boucher 2002;109:571 Epithelial cell layer Mucus layer Pericellular layer with cilia

Required Geometry for Effective Mucociliary Clearance Knowles & Boucher 2002;109:571

Consequences of CFTR Deficiency on Airway Clearance Knowles & Boucher 2002;109:571

Pathophysiology of CF Lung Disease CF Gene Mutation Ion Transport Abnormalities Altered Airway Environment Inflammation Infection TissueDamage R. Simon

Pathophysiology of CF Lung Disease Bronchiectasis Death Chronic Respiratory Failure CF Gene Mutation Recurrent Bronchitis Source Undetermined R. Simons

Clinical Manifestations Respiratory Tract Cough is the most constant symptom. Wheezing Recurrent chest infection Cyanosis is a late sign Atelactasis, hemoptysis, pneumothorax, and cor pulmonale Sinusitis, nasal polyps

Clinical Manifestations…. Intestinal Tract 1.Meconium ileus 10-20% 2.Meconium plug syndrome (meconium ileus equivalent)…more than 85% of patients showed evidence of maldigestion from exocrine pancreatic insufficiency. 3. Bile or acid reflux with oesophagitis 4. Sub acute appendicitis 5. Rectal prolapse 6. Failure to thrive 7. Fat-soluble vitamin deficiency manifestation.

Clinical Manifestations… Biliary Tract Biliary cirrhosis symptomatic in 2-3%. Ascitis, Jaundice, hematemesis, esophageal varices Neonatal hepatitis

Clinical Manifestations… Diabetes Mellitus… 8% after the age of % of males are azoospermic because of failure of development of wolffian duct structure. Secondary amenorrhea Cervicitis Hypochloremic alkalosis

Diagnostic criteria for CF At least one of the following: 1) One or more clinical manifestations of CF Meconium ileus Chronic bronchitis / bronchiectasis Chronic infection of the paranasal sinuses Pancreatic insufficiency Salt loss syndromes Male infertility due to congenital bilateral absence of the vas deferens 2) History of CF in a sibling

Diagnostic Criteria for CF At least one of the following: 1)Elevated sweat chloride test 2)Identification of a mutation in each CFTR gene known to cause CF

The Sweat Test “ Gold Standard ” for testing over 40 years - painless - inexpensive - gives definite answers Results; Cl - ≥ 60 mEq/L Positive mEq/L ?

Genotyping for CF Diagnosis 1601 CFTR mutations known to cause CF Only 25 mutations have a frequency > 0.1% Frequency, % R347P kbC  T Δ I507 R117H R1162X G  A R553X 621+1G  T W1282X N1303KG551DG542X ΔF508 CF Genetic Analysis Consortium Population Frequency of Specific CFTR Mutations Causing CF

CF Treatment PHYSIOTHERAPY and physical activity ANTIBIOTIC THERAPY BRONCHODILATOR THERAPY Beta2 agonist ANT-INFLAMMATORY AGENTS Corticosteroids for Bronchopulmopnary aspergillosis TREATMENT OF PULMONARY COMPLICATIONS

Hereditary Pulmonary Emphysema “alpha1 antitrypsin deficiency” Emphysema - abnormal permanent enlargement of the airspace distal to the terminal bronchioles, accompanied by destruction of their walls and without obvious fibrosis. Hereditary deficiency of α 1-antitrypsin inhibitor accounts for about 2% of emphysema cases. Alpha1 antitrypsin deficiency (AATD) is a autosomal recessive disorder characterized by a predisposition to emphysema and cirrhosis.

Alpha1 antitrypsin is a serpin peptidase inhibitor that protect connective tissue of the lungs from the elastase released by leucocytes. Liver damage arises not from the deficiency of the protease inhibitor, but from pathological polymerization of the variant alpha1-antitrypsin before its secretion from hepatocytes.

Pathogenesis of Lung Damage in AATD Clinical Case AAT

AATD is a Protein Folding Disease Protein folding is the process by which an unfolded polypeptide chain folds in to a specific native and functional structure Defective protein folding is an important mechanism underlying the pathogenesis of many diseases

More than 75 alleles of the α 1-antitrypsin inhibitor gene have been described. The three main phenotypes are ; MM (normal), MZ (heterozygous deficiency) and ZZ (homozygous deficiency).

Abnormal Folding and Polymerization of AAT The most common and severe form of AAT deficiency is caused by e Z mutation, a single base substitution (Glu-342-lys) in the AAT gene. This slows the rate of protein folding in the cell Allowing the accumulation of an intermediate which polymerizes Impeeding its release Leading to plasma deficiency AAT Polymer

Lung Related Clinical Manifestations Emphysema Presenting Symptoms : Dyspnea (most common symptom) Cough, phlegm production and wheezing Bronchodilator responsiveness Differences with patients w usual COPD Earlier Age Bullous changes prominent in lung bases > 90 % of ZZ phenotype have lung bases involved Limited to lung bases in 24 %Found exclusively in Asthma and Bronchiectasis: Relationship not proven

Diagnosis Measure AAT level Mutation analysis

Asthma Asthma is a disorder that causes the airways of the lungs to swell and narrow, leading to wheezing, shortness of breath, chest tightness, and coughing. Asthma is caused by inflammation in the airways. Interest in finding a genetic susceptibility locus is based on the heritability that asthma shows. Children with one asthmatic parent 3-6 times more likely to develop asthma than a child with two normal parents 1. Children with two asthmatic parents 10 times more likely to develop asthma than normal 1.

Asthma: a complex phenotype Clinical/Physiological phenotypes Phenotypes related to triggers Phenotypes related to inflammation Severity-defined Exacerbation-prone Chronic airflow limitation Treatment resistant Age at onset Aspirin Environmental. Allergens Occupational Allergens Menses Exercise Eosinophilic Neutrophilic Pauci-granulocytic Wenzel, Lancet, 2006 « Not a single disease entity but made up of various overlapping phenotypes … in people with different genetic predisposition & susceptible to different environmental triggers » OR « A symptom (as fever): the clinical manifestation of several distinct diseases

Strategies used to identify genes involved in asthma-related phenotypes Genome-wide screen approach Linkage studies ~ 400 genetic markers (microsatellites) Genome-wide association studies ~ genetic markers (SNP ) Candidate gene approach Fine mapping Associations Gene discovery Biological studies Hypothesis-driven No Hypothesis X Y

Regions most often replicated across populations RegionAsthmaAtopyIgEEOS BHRFEV 1 1p q p q q q Phenotype linked to several regions: polygenic? One region linked to several phenotypes: one pleiotropy gene or several genes in the same region? > 20 genome screens conducted to date Populations: Europeans +++, Australians, North-Americans, Chinese, Japanese

GENOME SCAN OF 295 EGEA FAMILIES for 8 asthma-related phenotypes Bouzigon et al, Hum Mol Genet 2004 EOS IgE MultiRAST SPT X Y IgE 12p13 SPT 17q22 FEV 1 SPTQ 21q21 FEV1 6q14 FEV 1 SPTQ Asthma BR

Candidate gene approach > 500 association studies of asthma phenotypes (Ober & Hoffjan 2006) 118 genes associated to asthma or atopy phenotypes 54 genes found in 2 to 5 independent studies 15 genes found in 6 to 10 independent studies 10 genes found in > 10 independent studies IL4, IL13, CD14, IL4RA, ADRB2, HLA-DRB1, HLA-DQB1, TNF, FCER1B, (ADAM33)

Pulmonary Fibrosis associated with known genetic causes Neuofibromatosis Hermensky Puldak Syndrome Gaucher Disease Niemann-Pick Disease Tuberous sclerosis