Block 13 Flashcards
Define: dyspnoea
Breathlessness
An unpleasant sensation of a feeling of an increased demand for breathing
What are some causes for breathlessness?
Pulmonary oedema Pneumothorax Pulmonary embolism Acute: - Anaphylaxis - Acute asthma - Pneumonia
Subacute:
- heart failure
- pleural effusion
- lung cancer
- anaemia
Slowly progressive:
- chronic bronchitis and emphysema
- interstitial lung disease
- pneumoconiosis
- pulmonary arterial hypertension
What are some causes of cough?
Airway/lung infection Left heart failure Lung cancer Foreign body inhalation ACE inhibitors Asthma Pulmonary fibrosis COPD
Risk factors for TB
Elderly Immunocompromised Diabetes Hodgkin lymphoma Chronic lung disease Chronic kidney failure Malnutrition Alcoholism
What are the pathological manifestations of TB?
Caseating granulomas
Cavitation
Describe secondary TB
Arises in previously sensitised host
Appears when host immune system compromised
Cavitation occurs readily
Erosion of cavities = coughing up bacteria = INFECTIOUS
Reactivation of latent infection or exogenous reinfection
What are some of the carcinogens that can cause lung cancer?
Radon Arsenic Asbestos Outdoor air pollution Cigarette smoke Hydrocarbons
What are some of the carcinogenic substances in cigarette smoke?
43 known
Carcinogenic metals - arsenic, nickel, cadmium, chromium
Potential promoters - acetaldehyde, phenol
Irritants - nitrogen dioxide, formaldehyde
Cilia toxins - hydrogen cyanide
What are the targets of genetic damage in cancer?
Growth promoting oncogenes
Growth inhibiting cancer suppressor genes
Genes that regulate programmed cell death
Genes that regulate repair of damaged DNA
What is the histology of normal respiratory epithelium?
Pseudostratified, columnar, ciliated
Squamous if damaged
Describe what is seen in dysplasia
Disordered cell growth
Loss of normal architecture and of uniformity of cells
Pleomorphic, hyperchromic nuclei
Increase in mitotic figures often at abnormal locations
Precedes but does not necessarily lead to cancer
Squamous cell carcinoma
Develops from squamous metaplasia
Excessive growth of abnormal squamous cells
Locally invasive
Able to form metastases
How does carcinoma of the lung present?
Cough (75%)
Weight loss (40%)
Chest pain (40%)
Dyspnoea (20%)
What are the local effects of lung cancer, what causes them?
Pneumonia, lobar collapse, abscess - obstruction of airway
Lipid pneumonia- obstruction
Pleural effusion - spread to pleura
Hoarseness - invasion of recurrent laryngeal nerve
Dysphagia - oesophageal invasion
Diaphragm paralysis - phrenic nerve invasion
Rib destruction - chest wall invasion
SVC syndrome - SVC compression
Horners syndrome - invasion of sympathetic ganglia (Pancoast)
What are the systemic effects of lung cancer?
Metastatic spreak
Ectopic production of hormones - ADH, ACTH, Parathyroid hormone, calcitonin, gonadotropins, serotonin
Peripheral neuropathy
Dermatological abnormalities
Haematological abnormalities
What are the 2 main subtypes in lung cancer?
Non small cell carcinoma 80%
Small cell carcinoma 20%
What are the 3 sub groups of non small cell carcinoma?
Squamous cell carcinoma 25-40%
Adenocarcinoma 25-40%
Large cell carcinoma 10-15%
Describe adenocarcinoma (lung)
Infiltration of lung by abnorma glandular structures
Shows glandular differentiation
- tubular/acinar/papillary structures
- Mucin production
Precursor lesions - atypical alveolar cell hyperplasia (alveoli lined by atypical cuboidal epithelial cells)
Describe small cell carcinoma (lung)
Shows neuroendocrine differentiation
Crowded small cells with hyperchromatic glassy nuclei and extremely scanty cytoplasm
What are the 2 main factors for rapid spread of TB?
Crowded living conditions
A population with little native resistane
Where is prevalence of TB highest?
China
India
Southern Africa
What is the incidence of TB in the UK?
13 per 100,000
Highest in London
What groups are most at risk of TB?
Alcoholics Intravenous drug users Homeless Prison inmates Urban poor
How is TB spread?
Inhalation of droplet nuclei
Aerosolised by coughing, sneezing or talking
8 hours of close contact required - prolonged exposure
Describe the process of TB infection
- Bacteria multiply freely in alveolar space or within macrophages
- Proceeds for weeks
- Development of tissue hypersensitivity
- CD4 recognise the antigens presented by macrophages
- Cytokine release
- Form Langhans giant cells (fused macrophages)
Describe caseous necrosis in TB
Inherently unstable
Liquifies and discharges through the bronchial tree producing a tuberculous cavity
Infectious material sloughed from a cavity can allow bronchogenic spread
What questions should be asked in taking a history from a patient with TB?
History of TB exposure Country of origin Age Ethnic or racial group Occupation
What is the presentation of TB?
Productive, prolonged cough (over 3 weeks) Chest pain Haemoptysis Fever Chills Night sweats Appetite loss Weight loss Fatigue
What happens in primary TB infection?
Rapid destruction of bacteria and the infective process is arrested (only evidence is positive ManToux test)
Ghon focus occurs but is stopped
What happens in post primary infection?
Immune deficiency which allows reactivation as macrophage and granuloma break up
Causes bronchial spread as necrosis occurs
Where are the main sites of spread for extra-pulmonary TB?
Can be to any organ
Abdomen Bone Brain Muscle Retina Lymph node
What percentage of TB cases are purely extrapulmonary?
19-30%
What is the stain used for acid fast bacilli?
Ziehl- Neelson
What tests can be used to check immunity to TB?
Man toux test (only specific for mycobacteria)
IFN-g (specific for TB)
What tests should be carried out if you suspect TB?
Chest X-ray Sputum specimens Routine drug susceptibility testing HIV testing Hepatitis testing
What are the first line drugs for TB treatment?
Isoniazid Rifampicin Pyrazinamide Ethambutol Rifabutin Rifapentine
Viractiv - one tablet for all 4 drugs
Name some occupational lung diseases
Occupational asthma COPD Pneumoconiosis Toxic pneumonitis Hypersensitivity pneumonitis Benign pleural disease e.g. asbestos Infective - TB
Outline occupational asthma
Underdiagnosed
Most common cause of occupational lung disease
Baker ,soldering, Paint spraying, animal housing.
Can prevent lifelong asthma if picked up early enough
Outline simple pneymoconiosis
Coal miners lung
Causes chronic bronchitis
Normal lung funtion
Cough and sputum
Outline silicosis
Coal workers (mixed) Sand blasters (pure)
Rare
Upper lobe nodules and lymph node calcification and enlargement
Predisposes to TB and lung cancer
Outline siderosis
Inhaled iron
Doesn’t cause disability or decrease lung function
Outline hypersensitivity pneumonitis
Form of pulmonary fibrosis (presents like pneumonia - breathing difficulties and fever)
Farmers lung (mouldy hay - fungal spores) and pigeon fanciers lung
Describe the pathogenesis of TB
- Macrophages are infected by mycobacterium tuberculosis
- Bacteria replicate within the macrophage
- 3 weeks post infection - TH1 response activates macrophages
- TH1 release IFN gamma.
- TH1 stimulates formation of granlomas and caseous necrosis
- Infection is controlled within the macrophages
- It can be reactivated or reexposed
Describe secondary TB
Arises in previously sensitised host
Reactivation when immune system decreased or re-exposure
What are the clinical features of secondary TB?
Insidious in onset Malaise Anorexia Weight loss Low grade fever Sputum Haemoptysis
Describe the morphology of TB
- Small area of white inflammation with consolidation - Ghon focus
- Centre undergoes caseous necrosis
- Ghon complex = lung lesion and node involvement
- It undergoes progressive fibrosis then calcification (Ranke complex)
Outline miliary pulmonary disease
Occurs when organisms drain through lymphatics
Consolidation scattered throughout lungs
Define chronic bronchitis
Defined clinically as persistent cough with sputum production for at least 3 months in at least 2 consecutive years
What can result from persistent chronic bronchitis?
Progress to COPD
Lead to cor pulmonale and heart failure
Cause atypical metaplasia and dysplasia of respiratory epithelium
What is the pathogenesis of chronic bronchitis?
Long standing irritation of inhaled substances
Hypersecretion of mucus in large airways (hypertrophy of glands)
Proteases released from neutrophils
Marked increase in goblet cells
Damage to cilia and epithelium
Outline the morphology of chronic bronchitis
- Hyperaemia, swelling and oedema of mucous membranes
- Excessive mucinous secretions
- Hyperplasia of mucous glands
- Increased Reid index
- Marked narrowing of bronchioles
- Obliterations of lumen due to fibrosis (extreme)
What are the clinical features of chronic bronchitis?
Persistent cough, productive of sputum Dyspnoea on exertion Hypercapnia Hypoxaemia Mild cyanosis Impairment of respiratory function
What are the changes seen in chronic bronchitis?
Squamous metaplasia Glandular hyperplasia Goblet cell hypertrophy Smooth muscle cell hypertrophy Mucociliary dysfunction
LYMPHOCYTES not eosinophils
What is the incidence of lung cancer?
Occurs most frequently between 40-70 years
Peak incidence at 50-60
5 year survival rate = 16%
Incidence and mortality rates have been decreasing
Outline pathogenesis of lung cancer
Stepwise accumulation of genetic abnormalities
- 87% are smokers
- Heavy smokers (10 pack years) are 60x increased risk
- Gene mutations: KRAS, EGFR, p53, RB1, p16
What are the features of a lung adenocarcinoma?
Malignant epithelial tumour with glandular differentiation
Most common in women and non-smokerss
Peripheraly located and tend to be smaller
Slow growth - wide and early metastasis
KRAS mutation
What are the features of a small cell carcinoma?
Highly malignant with distinctive cell type - high mitotic count
No cell differentiation, necrosis is common and extensive
Neuroexcretory granules
Strong relationship to cigarette smoking
p53 and RB1
What are the features of a squamous cell carcinoma (lung)
Most common in men
Closely correlated with smoking
Keratinisation
p53 mutations
What are the uses of radiotherapy in lung cancer?
External radiotherapy (more common) and internal during bronchoscopy
Shrink tumour blocking an airway
SE: fatigue, anaemia, skin soreness, hair loss in area, difficulty swallowing
What are the uses of chemotherapy in lung cancer?
Small cell lung cancer
Can be used for non-small cell after surgery
SE: tiredness, nausea and vomiting, mouth ulcers, diarrhoea, constipation, hair loss, increased infection
What are the uses of surgery in lung cancer?
Non-small cell lung cancer Lobectomy Sleeve resection Pneumonectomy Segmentectomy
Mycobacterium tuberculosis
large non-motile baccili obligate aerobe (upper lobes) Intracellular parasite of macrophages Acid fast High lipid content
Why is the high lipid content of M. tuberculosis important?
Impermeability to stains and dyes
Resistance to many antibiotics
Resistance to killing by acidic and alkaline compounds
Resistance to osmotic lysis via complement deposition
Resistance to lethal oxidations and survival inside macrophages
Define multi-drug resistant TB
Resistant to at least 2 of the best anti-TB drugs
Isoniazid and rifampicin
Define extensively drug resistant TB
XDR TB
Rare
Resistant isoniazid and rifampicin plus resistant to any fluroquine and at least 1 of 3 injectable 2nd line drugs e.g. kanamycin, capremycin
Define asthma
Chronic inflammatory disorder of the airways that causes recurrent episodes of wheezing, breathlessness, chest tightness and cough, particularly at night and//or in early morning.
What are the hallmarks of asthma?
Increased airway responsiveness to various stimuli
Causing episodic bronchoconstriction
Inflammation of bronchial walls
Increased mucus secretion
What are the common triggers of asthma?
Respiratory infections Environmental exposure to irritants (smokes, fumes) Cold air Stress Exercise
What are the 4 different types of asthma?
Atopic
Non-atopic
Drug-induced
Occupational
What is atopic asthma?
Type 1 IgE mediated hypersensitivity reactions
- Begins in childhood
- Positive family history common
- Triggered by allergens
What is non-atopic asthma?
- Respiratory infections are common triggers
- Hyperirritability of bronchial tree
- Virus induced inflammation lowers threshold of the subepithelial vagal receptors to irritants
Describe the pathogenesis of asthma
- Genetic predisposition for atopy
- Initial sensitisation to allergen which stimulates production of TH2 cells
- TH2 cells secrete cytokines IL4, 5 and 13
- Promotes inflammation and stimulates B cells to produce IgG and the antibodies
- IgE, eosinophils and mucus secretion
- IgE coats mast cells, repeat exposure to release granule contents
Describe the early phase reaction in asthma?
Bronchoconstriction - triggered by direct stimulation of subepithelial vagal receptors
Increased mucous production
Variable degrees of vasodilation
Increased vascular permeability