Restrictive lung diseases are caused by decreased lung volumes without airflow obstruction. The restriction occurs due to pathology in the lung parenchyma, chest wall, or pleura. Restrictive patterns are seen in interstitial lung disease, morbid obesity, scoliosis, kyphosis, ankylosing spondylitis, and neuromuscular disorders such as Guillain-Barre syndrome, myasthenia gravis, muscular dystrophy, and ALS.
| Chest wall disorders | Kyphoscoliosis, morbid obesity, pleural disorders |
| Lung parenchymal disorders | Interstitial lung diseases (pneumoconiosis, sarcoidosis, rheumatoid arthritis, collagen vascular diseases etc.) |
Interstitial lung disease (ILD) includes more than 200 different disorders. In ILD, inflammation can lead to fibrosis. The trigger for the initial inflammation is not always known, but several exposures and conditions predispose to ILD, including bleomycin, asbestos, silica, tobacco smoke, wood dust, mold, environmental allergens, and autoimmune diseases.
Cytokines and proteases released by activated inflammatory cells, along with ROS, damage alveolar cells. This is followed by proliferation of type II pneumocytes and repair by fibrosis. As fibrosis progresses:
Clinical presentation typically includes gradually progressive dry cough, dyspnea, tachypnea, cyanosis, and late inspiratory crackles. On gross examination, the lung is scarred with scattered cystic air spaces, producing a “honeycombing” pattern. CxR shows diffuse bilateral reticulonodular opacities.
Pneumoconiosis are a group of mostly occupational diseases caused by inhalation of dust that leads to ILD. Inhaled particles <1 micrometer can reach the alveoli and trigger an inflammatory response in susceptible individuals.
| Occupational exposure | Type of pneumoconiosis |
| Coal dust | Coal worker’s pneumoconiosis, Caplan’s syndrome, progressive massive fibrosis |
| Silica | Silicosis, Caplan’s syndrome |
| Asbestos | Asbestosis |
| Beryllium | Berylliosis |
| Mouldy hay, grain | Farmer’s lung (Saccharopolyspora rectivirgula) |
| Molasses, sugarcane (bagasse) | Bagassosis (T.vulgaris) |
| Cotton, hemp, flax | Byssinosis, cotton worker’s lung |
| Bird droppings, feathers | Bird fancier’s lung |
| Silo-Filler’s disease | Exposure to NO2 gas in silo causes pulmonary edema |
1) Coal worker’s pneumoconiosis (CWP): CWP develops in coal miners after 20-30 years of exposure. Alveolar macrophages and cytokines (IL 1, TNF, and PDGF) are implicated in inflammation and fibrosis. Miners are at higher risk of TB and RA, but the risk of lung cancer is the same as in the general population. Clinical features include cough with black sputum, dyspnea, and cor pulmonale. Two types are seen:
Simple CWP: Scattered foci of dust-laden macrophages with surrounding dilated air spaces are seen. Fibrosis is minimal and the disease is mostly in the upper zones. CxR shows round nodular opacities with occasional calcification.
Progressive massive fibrosis or complicated CWP: Larger lesions than in simple CWP are present, with necrotic areas and severe fibrosis that obliterates the respiratory bronchiole and vessels. Alveoli are markedly dilated. CxR shows large opacities that may be surrounded by cystic spaces.
Caplan’s syndrome: Rheumatoid arthritis plus CWP or pneumoconiosis is called Caplan’s syndrome. Rheumatoid nodules are seen in the lung. Microscopically, these are firm nodules with an inflammatory exudate of mononuclear cells and fibroblasts, with cavitation and necrosis.
Anthracosis is a common finding in city dwellers and results from deposition of anthracotic (carbon) dust pigment in the lungs due to pollution and cigarette smoke. Pigmented macrophages called “dust cells” can be seen in alveoli, respiratory bronchioles, and draining lymph nodes in anthracosis.
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