pathology of the respiratory system 2

PATHOLOGY OF THE RESPIRATORY SYSTEM

BY

CHAPIMA F.MSc. PTH - Clinical Pathology (UNZA), B.Sc. (UNZA)

Lecture outline Normal lung Pathology

Congenital anomalies of the lung Atelectasis Obstructive pulmonary diseases Restrictive pulmonary diseases Pulmonary infections Lung tumours

CONGENITAL DISORDERS Congenital anomalies of the lungs commonly

present within the first 2 years of life and frequently manifest with respiratory distress and cyanosis

1. Laryngeal Web This is the partial opening of the larynx. A membranous web forms at the level of the

vocal cords, partially obstructing the airways.

2. Laryngotracheal stenosis/Atresia

Laryngotracheal stenosis refers to abnormal

narrowing of the central air passageways.

This can occur at the level of the larynx,

trachea, carina or main bronchi.

Rare

Usually associated with some

tracheoesophageal fistula.

3. Pulmonary Sequestration

Pulmonary Sequestration is the presence of a

lung tissue not connected to the airway system.

It can be located in the thorax or

mediastinum

Its blood supply comes directly from the aorta or

its branches and not from the pulmonary

arteries.

Pulmonary Sequestration……….

Types

2 types are noted

Intralobar Sequestration – the lung tissue is

enclosed within the pleura of the normal lung.

Usually it is located in the lower lobes and

60% on the left lung.

Pulmonary Sequestration………..

Extra lobar Sequestration

The lung tissue is separated from the pleural

covering.

May be found anywhere in the thorax or

mediastinum and they are associated with

polyhydramnios

ATELECTASIS (LUNG COLLAPSE)

Definition:

AKA collapsed lung refers to the collapse of a

previously expanded lung tissue.

Major types

It is classified according to the cause;

Obstructive Atelectasis

Compression Atelectasis

Contraction (Scar) Atelectasis

Atelectasis………..

Obstructive

Atelectasis occurs

when an obstruction

prevents air from

reaching distal airways

e.g. aspiration of a

foreign body.

Atelectasis………..

Compression

Atelectasis

Due to fluid, air, blood,

or tumor in the pleural

space Compression Atelectasis

Atelectasis………..

Contraction (Scar)

Atelectasis

Occurs when there is either

local or generalized fibrotic

changes in the lung or pleura

which hampers expansion of

the lung during expiration.

Atelectasis………..

All types of Atelectasis (except contraction) are

potentially reversible.

The best treatment is to treat the cause.

CHRONIC OBSTRUCTIVE PULMONARYDISEASE

COPD is a group of lung diseases that makes it

hard to breathe out.

Three major diseases are encountered in clinical

situations:

Chronic Bronchitis

Emphysema

And Asthma

1. Chronic bronchitis

Definition

Defined clinically as a productive cough for at

least 3 consecutive months for at least 2

consecutive years.

Highly associated with cigarette smoking

(90%) and air pollution.

Etiopathogenesis………..

Cigarette Smoking affects the lung in a number of ways;

1. It impairs ciliary movement.

2. It inhibits the function of alveolar macrophages.

3. It leads to hypertrophy and hyperplasia of mucus secreting glands as a result there is increased secretion of mucus which leads to obstruction of small airways.

Etiopathogenesis………..4. It also stimulates the Vagus nerve and causes

bronchoconstrictionClinical findings Persistent productive cough of long duration Dyspnea more on exertion Cyanosis Edema Chest painsPulmonary function tests show; Increased pulmonary resistance Reduced expiratory flow rates

Gross Morphologic features

The bronchial wall is

thickened, hyperemic and

edematous.

Lumina of the bronchi and

bronchioles may contain

mucus plugs and purulent

exudate.

Complications

Recurrent chest infections

Pulmonary HTN leading to right heart failure

(cor-pulmonale)

Lung cancer

2. Emphysema

Definition

Is an abnormal permanent enlargement of the

airspaces distal to the terminal bronchiole,

accompanied by destruction of their walls.

Classifications

Emphysema is classified according to its

anatomic distribution within the lobule.

Classifications………..

Four major types of emphysema exists but

only the first two cause clinically significant

airway obstruction.:

Centroacinar Emphysema: Dilation is limited

to the central or proximal parts of the acini.

Panacinar emphysema: there is dilatation of

the entire acinus.

Classifications…………..

Classifications……………

Distal acinar emphysema: Dilation involves

mainly the distal part of the acinus.

Irregular emphysema: the acinus is irregularly

involved and is usually a complication of various

inflammatory processes.

Pathophysiology

Emphysema depends on the balance between

proteolytic enzymes, such as elastase and

antiproteinase-antielastase activities of α1-

antitrypsin.

Elastase if not neutralized by anti-elastase

will induces destruction of elastin causing

emphysema.

Pathophysiology …………..

Cigarette smoking causes emphysema by

attracting neutrophils and macrophages,

which are sources of elastase.

It also inactivates α1-antitrypsin.

Morphology

Cut surface of the lung shows distended air

spaces in the lobules.

Morphology…………….

Morphology…………….

Morphology…………….

Microscopic

There is distension and

destruction of the respiratory

bronchiole in the lobules

surrounded peripherally by

normal uninvolved alveoli.

Clinical features

Progressive dyspnea

Scant sputum production

Increased total lung capacity: due to increase in

residual volume from air trapped in the lungs

and Decreased FEV

Complications

Chronic bronchitis.

Pneumothorax due to the rupture of a surface

bleb.

3. Bronchial asthma

Definition

This is a Chronic Inflammatory disorder of the

airways that causes recurrent episodes of

wheezing, breathlessness, chest tightness, and

cough, particularly at night and/or in the early

morning.

Types

Extrinsic (immune, atopic or allergic)

asthma.

Disease begins in childhood, usually in patients

with a family history of allergy

Types……….

Intrinsic (non-immune, non-atopic) Asthma

or adult type) asthma includes asthma

associated with chronic bronchitis, as well as

other asthmas induced by exercise - or cold-

induced.

It usually begins in adult life and is not

associated with a history of allergy.

Types…………

Mixed asthma, which has characteristics of

allergic and idiopathic asthma.

Mixed asthma is the most common form.

Pathophysiology

The pathophysiology of bronchial asthmatic

attack is related to the release of chemical

mediators in an IgE and mast cell interaction.

When the antigen enters the air ways, IgE are

produced against these antigens which binds or

interacts with mast cells.

The mast cells ruptures and release chemical

mediators such as histamine.

Pathophysiology …………

The release of histamine results in:- Bronchospasm (rhythmic squeezing of the

airway). Production of abnormal amount of thick

mucus and initiates Inflammatory response, including increased

capillary permeability and mucosal edema.

Pathophysiology …………..

Narrowing of the air ways leads to;

Difficulty of expiratory phase of respiration

Retention of expired air in the alveoli & lung -

hyper inflation.

Signs and symptoms

Dyspnea

Wheezing on expiration caused by narrowing of

the airways.

Complications

Status asthmaticus

Superimposed chest infections

Chronic bronchitis

Emphysema

Death can result

RESTRICTIVE PULMONARY DISEASES

Restrictive pulmonary diseases are

abnormal conditions that are characterized by

reduced expansion of the lung and reduction in

total lung capacity.

It leads to difficulties in the inspiratory phase of

respiration.

Restrictive lung diseases…………

Restrictive lung diseases can be due to;

Chest wall disorders.

Interstitial and infiltrative lung diseases.

Restriction due to chest wall disorder

Kyphosis, Poliomyelitis

Pleural diseases

Restriction due to interstitial and infiltrative lung diseases

AKA interstitial lung diseases (ILDs), these are

diseases characterized by non-infectious lung

diseases.

They are referred to as Pneumoconiosis.

Pneumoconiosis

It is an environmental disease caused by inhalation of inorganic dust particles.

They are characterized by permanent retention of inhaled particles, which results in inflammation and fibrosis of the lung.

The major conditions include; Silicosis due to silica dust inhalation Asbestosis due to inhalation of asbestos fibers Anthracosis due to carbon inhalation

1. Anthracosis

Anthracosis is caused by

inhalation of carbon dust.

It results in irregular black

patches visible on gross

inspection.

It is common in urban areas

and causes no harm.

2. Silicosis

Silicosis is a chronic

occupational lung

disease caused by

exposure to free silica

dust

It is seen in miners,

glass manufacturers,

and stone cutters.

Advanced silicosis Scarring has contracted the upper lobe into a small dark

mass (arrow). Note the dense pleural thickening.

3. Asbestosis

Asbestosis is caused by inhalation of asbestos

fibers.

This disease is initiated by uptake of asbestos

fibers by alveolar macrophages.

A fibro-blastic response occurs from the release

of fibroblast-stimulating growth factors by

macrophages.

Asbestosis…………

This leads to diffuse

interstitial fibrosis, mainly in

the lower lobes.

Asbestosis results in marked

predisposition to

bronchogenic carcinoma.

Asbestos-related pleural plaques. Large, discrete fibrocalcific plaques are

seen on the pleural surface of the diaphragm.

PULMONARY INFECTIONS

1. PNEUMONIA Pneumonia is an inflammation of the lung

parenchyma.

It is characterized by; Chills and fever Productive cough Blood-tinged or rusty sputum Chest pains - Pleuritic in nature Shortness of breath and cyanosis

Classifications

Pneumonia is classified according to the cause

or morphologically.

According to the cause it can be;

Bacterial pneumonia

Streptococcus pneumoniae

Staphylococcus aureus

Klebsiella pneumonia

Classifications…………….

Pseudomonas aeruginosa

Viral pneumonias with Haemophilus influenza

especially type A as the usual causative

organism.

Fungal pneumonia - Pneumocystis jiroveci

(carinii) pneumonia is the most common

opportunistic infection in patients with AIDS.

Classifications…………….

Morphologically it can be classified as;

Lobar pneumonia

Bronchopneumonia or

Interstitial pneumonia

Lobar pneumonia

Lobar pneumonia is an acute

bacterial infection of a part of a

lobe, the entire lobe, or even two

lobes of one or both the lungs.

Causative organisms

Streptococcus pneumoniae more than 90% of all

lobar pneumonias

The other 10% may be caused by;

Staphylococcus aureus

β-hemolytic streptococci

Haemophilus influenza

Klebsiella pneumoniae

Morphological stages

If untreated, may follow 4 morphological

stages:

Congestion

Red hepatization

Gray hepatization and

Resolution

Morphological stages…………..

Congestion

This is the initial phase.

It represents the early acute

inflammatory response to

bacterial infection and lasts for

1 to 2 days.

Lungs are dark, red and wet.

Morphological stages…………..

Red hepatization

The term hepatization refers to liver-like consistency of the affected lobe on cut section.

This phase lasts for 2 to 4 days.

Lungs are solid, red and dry.

Morphological stages…………..

Gray hepatization

This phase lasts for 4 to 8

days.

The lungs are solid and

grey due to high

concentration of neutrophils in

the affected lung.

Morphological stages…………..

Resolution This stage begins by 8th to 9th day if no

treatment is given and is completed in 1 to 3 weeks.

However, antibiotic therapy induces resolution on about 3rd day.

The previously solid fibrinous constituent is liquefied by enzymatic action, eventually restoring the normal ventilation in the affected lobe.

Complications

Pleural effusion

Empyema

Lung abscess

Metastatic infection

Septicaemia

Bronchopneumonia

Bronchopneumonia is caused

by a wide variety of organisms.

It is characterized by

consolidated areas of acute

suppurative inflammation.

Bronchopneumonia……..

Interstitial pneumonia

Interstitial (primary atypical) pneumonia is

caused by various infectious agents, most

commonly Mycoplasma pneumoniae or

viruses.

It is characterized by diffuse, patchy

inflammation localized to interstitial areas of

alveolar walls.

2. LUNG ABSCESS

This is a localized area of suppuration within the

parenchyma.

Predisposing factors

Aspiration of micro-organisms due to loss of

consciousness from alcohol or drug overdose

Infections e.g. pneumonia

Clinical manifestations

Includes;

Fever, chest pains

Productive cough with a foul-

smelling purulent sputum

Radiographic evidence of a

fluid-filled cavity.

Cut surface – abscess seen

3. PULMONARY TUBERCULOSIS

Definition - It is an infection of the lung with

Tubercle bacilli.

it is spread by inhalation of droplets containing

the organism tubercle bacillus (also referred to

as the Mycobacterium tuberculosis).

Classifications

Primary tuberculosis is the initial infection,

characterized by the primary, or Ghon complex

(The lesions consist of a calcified focus of

infection and the hilar lymph nodes).

Secondary tuberculosis usually results from

activation of a prior Ghon complex, with spread

to a new pulmonary or extrapulmonary site.

Clinical features

Include;

Coughing

Chest pains

Fever

Hemoptysis

Pleural effusion and generalized wasting

Pathologic changes

Localized lesions usually in the apical or

posterior segments of the upper lobes.

Involvement of hilar lymph nodes is also

common.

Tubercle formation - The lesions frequently

coalesce and rupture into the bronchi.

Pathologic changes ………..

The caseous contents may liquefy and be

expelled, resulting in cavitary lesions.

Cavitation is a characteristic of secondary, but

not primary, tuberculosis; caseation (a

manifestation of partial immunity) is seen in

both.

Scarring and calcification

Primary pulmonary tuberculosis, Ghon complexThe gray-white parenchymal focus is under the pleura in the

lower part of the upper lobe. Hilar lymph nodes with caseation are seen on the left.

Milliary TB

LUNG CANCER

Definition

Malignant tumors of the lung’

Epidemiology

Rate of increase in lung cancer is declining in

men but increasing in women: peak incidence is

55-65 years of age.

Classifications

Most lung tumors are malignant.

LC can be classified as;

1. Primary lung cancer

2. Secondary lung cancer (metastatic cancer)

Metastatic cancer - is the most frequent lung

cancer than primary lung cancer.

Classifications ……………

For therapeutic purposes, primary

carcinomas are subdivided into;

Non-small cell carcinoma (75% of cases)

Small cell carcinoma (20% of cases)

Non-small cell carcinomas usually respond to

surgery

Whereas small cell carcinomas are usually

inoperable.

Predisposing factors

Cigarette smoking – it is directly proportional in incidence to the number of cigarettes smoked daily and to the number of years of smoking.

Other factors; Air pollution Radiation; incidence increased in radium and

uranium workers Asbestosis Industrial exposure to nickel

Clinical findings

Cough: most common symptom

Dyspnea

Hemoptysis

Weight loss

Chest pain

Gross Morphology

Sites of metastasis of primary cancer

Adrenal gland

Liver

Brain

Bone

References

Emanuel Rubin, and John L. Farber, Essential Pathology, Philadelphia,

1990

William Boyd; Textbook of Pathology, structure and Function in disease,

Philadelphia, 8th edition, 1987

Macfarlane, Reid, Callander, Illustrated Pathology, Churchill

Livingstone, 5th edition, 2000.

Cotran RS, Kumar V, Collins T. Robins pathologic basis of diseases.

Philadelphia, J.B. Saunders Company. 6th edition. 1999

Muir’s Textbook of Pathology 15th edition