Page 389 - Concise Pathology for Exam Preparation ( PDFDrive )

374 SECTION II Diseases of Organ Systems

loss. There is consolidation of peripheral lung substance which is infiltrated by lym-
phocytes and eosinophils (inflammatory cells are present within the alveoli and in the
alveolar septae.

Q. Write briefly on smoking-associated interstitial disease.
Ans. Interstitial lung disease associated with smoking includes
1. Desquamative interstitial pneumonia (DIP): Airspaces contain aggregates of macro-
phages which were earlier thought to be desquamated pneumocytes which is why the
entity was named DIP. It presents insidiously between 40 and 50 years in smokers with
dyspnoea and cough and is steroid responsive.
2. Respiratory bronchiolitis-associated interstitial lung disease: A bronchiocentric
condition which is typified by peribronciolar chronic inflammation and fibrosis. Pig-
ment containing macrophages are present in the respiratory bronchioles and the patient
presents with dyspnoea and cough.

Q. Write briefly on pulmonary alveolar proteinosis (PAP).

Ans. PAP results from a defect in pulmonary macrophage function which results in im-
paired removal of surfactant from the alveolar and bronchiolar spaces.

Salient Features of PAP
• Rare disease characterized by a defect in GM-CSF or macrophage function
• There is intra-alveolar or intrabronchiolar accumulation of surfactant
• Patient presents with cough and expectoration of gelatinous material
• Histopathology shows consolidation of lung substance due to presence of surfactant
containing PAS positive precipitate in the alveolar spaces. There is minimal inflamma-
tion with presence of cholesterol clefts.
• PAP may be
1. Autoimmune: Presence of neutralizing antibodies to GM-CSF. Reduced or absent
GM-CSF signalling interferes with the terminal differentiation of the alveolar macro-
phages which in turn impairs their ability to catabolize surfactant
2. Secondary: Occurs secondary to a variety of conditions (hematopoietic
disorders, immunodeficiency syndromes, inborn errors of metabolism and acute
silicosis
3. Hereditary: Rare neonatal condition caused by GM-CSF receptor gene mutations

Q. Describe the clinicopathological features of occupational lung
diseases.
Ans. Occupational lung diseases are a reaction of the lung to inhalation of mineral dusts
encountered in the workplace.
• Factors which determine the extent of damage caused by the inhaled dust:
• Size and shape of the particle
• Their solubility and physiochemical composition
• The amount of dust retained in the lung
• The additional effect of other irritants, such as tobacco smoke
• Host factors, such as efficiency of clearance mechanism and immune status of the
host
• The tissue response to inhaled dust may be of the following three types:
• Formation of fibrous nodules
• Interstitial fibrosis
• Hypersensitivity reaction
Diseases caused by air pollutants (Table 13.4)

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