Non-neoplastic lung disease.

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This is a complex heterogeneous group of disorders, all with impaired lung function of a persistent and debilitating quality.

Asthma.

This reversible airway outflow obstruction produces over distended lungs with excess mucus secretion and may follow atopic (type 1 hypersensitivity) occupational (type 3 hypersensitivity) and/or allergic phenomena usually in relation to aspergillosis. There is also a group of patients who are sensitive to factors such as aspirin, cold temperatures, infections, stress, exercise and various pollutants. In addition, variable dusts, pollens, food stuffs etc may provoke asthmatic attacks. There is often a family history. Increased bronchial tone and excessive mucus secretion reflect inflammatory events (mast cells, lymphocytes, eosinophils) and increased oedema due to an increase in vascularity. Histologically, this is not usually biopsied but when samples are taken there is often an increase in smooth muscle, and increase in basement-like material and excessive mucus glands. Autopsy, unfortunately, is the commonest reason to sample asthmatic lungs. A variety of cytokines and chemokines are relevant in terms of the initiation of the early and subsequent late phase.Occupational asthma reflects an individual sensitivity to a work place-based irritant, probably as a result of type 1 and type 3 hypersensitivity mixed.

Obstructive pulmonary disease

It is subclassified into acute obstruction and chronic.

Acute airway obstruction may be life threatening and acute, or slowly progressive, but nevertheless significant and life threatening. Acute obstruction generally reflects tumours or foreign bodies with distal collapse of the lung. However, this may progress to subsequent bronchiectasis and significant chest sepsis.

Chronic obstructive airways disease is subdivided in to chronic bronchicitis, emphysema, asthma (vs) and bronchiectasis.

Chronic bronchitis.

It is to a degree reversible and intermittent, but is diffuse producing significant alteration to lung function with a reduced VC capacity, reduced FEV1/FVC ratio and a reduced PEFR. There is a clinical diagnosis of persistent cough and sputum for more than three months in two consecutive years. Mucus oversecretion, bronchial gland hypertrophy, respiratory bronchiolitis may all be seen. It has a strong link to tobacco smoking. It is also aggravated by pollution and infections. With time, the patient progresses to significant carbon dioxide retention, hypoxia and progressive right side cardiac failure. There is some similarity of asthmatic pathology but more accentuated fibrosis and destruction of local tissues. Mucus plugging and mural weakness is often seen with local squamous metaplasia and chronic inflammation. Goblet cell hyperplasia is often seen, reflecting the excess mucus secretion.

Emphysema

This revolves around the loss of lung tissue, principally at the alveolar level although there is an effect in the respiratory bronchiole tissues as well. It is often associated with chronic bronchitis, and has similar tobacco smoking aetiology. Subdivided into centri-acinar, pan-acinar and distal acinar types, it may also reflect alpha-1-antitrypsin deficiency, coal dust exposure (coal workers’ pneumoconiosis), cadmium toxicity etc. The prime pathology revolves around inflammatory mediators releasing matrix destructive enzymes resulting in tissue damage and loss of alveolar and related tissue supports. It may progress to large bullae. Bullous emphysema is particularly troublesome as it produces significant gas trapping.The patient progresses to significant pulmonary hypertension reflecting poor oxygen delivery to tissues.

Bronchiectasis.

This is a permanent dilation of bronchi and bronchioles due to obstruction and severe inflammation. The pooling of secretions may predispose to repetitive chest infections, foul smelling sputum, haemoptysis and an increased risked of atypical infection (fungus). Subdivided into cylindrical, secular and fusiform, the pathology is that of local destruction of support tissues with resultant fibrosis and airway dilation. It is associated with current chest sepsis, septicaemia, metastatic abscess formation and on occasion amyloid. Progression to right side cardiac failure is also recognised.

Interstitial lung disease.

This is a complex group of disorders with a reduced TCO, VC and FEV1. There is a relatively normal FEV1/FVC ratio and a normal PEFR. In practical terms there is an increased band of fibrous tissue within the lung parenchyma resulting in increased stiffness and decreased expansion. There are numerous causes and a variety of patterns. Treatment is often very limited, and revolves around steroids and immunosuppressive agents. Ultimately, lung transplantation may be required.

Acute interstitial diseases include adult respiratory distress syndrome, drug/toxin reactions, radiation pneumonitis and diffuse intra-pulmonary haemorrhage.

ARDS. This often is a multi-system disorder eventually following significant lung acute injury, protein exudation, loss of gas transfer and a variety of inflammatory changes. There are numerous causes including shock, trauma, infections, toxic gasses, narcotics, radiation, gastric aspiration and oxygen toxicity (neonates).

Drugs are particularly troublesome for some peoples lungs. There are those with recognised side effects (Busulfan/Bleomycin) together with some toxins (Paraquat). In general terms these revolve around generation of superoxide free radicals.

Radiation pneumonitis also reflects superoxides and local direct tissue toxicity.

Chronic interstitial lung diseases include a whole range of disorders.

The prime players amongst this group are usual interstitial pneumonia/cryptogenic fibrosing alveolitis, pneumoconioses (occupational lung disease), sarcoid, diffuse malignancies, rheumatoid disease, etc.

Idiopathic pulmonary fibrosis (aka cryptogenic fibrosing alveolitis) is a diagnosis of exclusion. The progressive fibrosis limits the patients ability to respire, and usually ends up with a terminal chest infection and hypoxic damage. Progressive right side cardiac failure is seen and the lungs show a honeycomb architecture with diffuse fibrosis and a pleural bias. Histologically there is a variable pattern of inflammation and fibrosis, which is often designated usual interstitial pneumonia (UIP).

Other patterns of interstitial pneumonia also exist (non-specific interstitial pneumonia (NSIP), respiratory bronchiolitis interstitial lung disease (RBILD), giant cell interstitial pneumonia (GIP), lymphocytic interstitial pneumonia (LIP), desquamative interstitial pneumonia (DIP) etc. These are outside the scope of presentation. But in simple terms show a different pattern histologically, that may indicate a different response to immunosuppressives and a different aetiology.

Of importance Langerhan’s cell histiocytosis ( LCH, aka histiocytosis X) is associated with a cystic and fibrotic process of the lung with a characteristic radiological image. It may be localised to the lung or more diffuse systemically.

Pneumoconiosis. This lung disorder group usually reflects inhaled dusts/toxins.

Coal workers’ pneumoconiosiscan be seen as heavy dust comination through to lung nodularity, progressive massive fibrosis, and an increased risk of chronic obstructive disease. Many areeligible for compensation if diagnosed.Coal workers pneumoconiosis has no increased risk of cancer.

Silicosis, usually reflects silica exposure and may occur in grinding related occupations as well as to a degree other mining practices (including coal mining).Silicosis is also associated with an increased risk of tuberculosis. There is a borderline increase in the risk of cancer.

Asbestos exposure may lead to malignant mesothelioma and lung cancer with regard to chest neoplasia. However, it is also associated with persistent pleural effusion, diffuse pleural fibrosis and diffuse interstitial lung fibrosis (UIP pattern). Other pneumoconiosis includes extrinsic allergic alveolitis in relation to inhaled allogens producing a type 3 hypersensitivity reaction.Pleural plaques are associated with asbestos exposure but are not associated with lung cancer or mesothelioma induction.

Rare patterns of extrinsic allergic alveolitis include byssinoisis due to cotton fibre, bagassosis due to sugar cane fibre and bird fanciers lung due to bird faeces. Farmers (farmers’ lung) may suffer a similar reaction due to mouldy hay and Aspergillus spores. These all usually produce an acute inflammatory reaction with associated dyspnoea, but if the exposure is persistent then progressive fibrosis can occur in association with giant cell granulomas containing cholesterol crystals.

Sarcoidosis. This is an idiopathic granulomatous reaction with associated granulomas within the lymph nodes and lung parenchyma. There is an associated fibrotic reaction that can be mimicked by Berylliosis (beryllium pneumoconiosis).

Rheumatoid arthritis has an association with lung disease, usually with a pattern paralleling usual interstitial pneumonia.

Diffuse infiltrating malignancy, involving the lymphatics produces lymphangitis (carcinomatosa) with a progressive stiffening of the lung tissues, increasing oedema and subsequent fibrosis. Bronchiolo-aveolar carcinomacan also diffuse infiltrate and diffusely infiltrate the lung tissue producing local fibrosis.