A worker in a stone quarry develops progressive dyspnoea over 15 years. Chest X-ray shows bilateral upper lobe fibrosis with egg-shell calcification of hilar nodes. Which lung function test finding is MOST characteristic of this condition?
- A Obstructive pattern — reduced FEV1/FVC ratio
- B Mixed obstructive-restrictive pattern only in advanced disease
- C Restrictive pattern — reduced FVC with preserved FEV1/FVC ratio ✓
- D Normal spirometry with isolated DLCO reduction
Explanation
Silicosis (caused by crystalline silica inhalation in quarry/mining workers) classically produces a restrictive ventilatory defect on spirometry — reduced total lung capacity (TLC), reduced FVC, with preserved or increased FEV1/FVC ratio — due to diffuse pulmonary fibrosis reducing lung compliance. Eggshell calcification of hilar nodes is pathognomonic of silicosis. When complicated by emphysema (progressive massive fibrosis), a mixed pattern may occur. The DLCO is reduced due to impaired gas exchange from fibrosis, but the primary spirometric pattern is restrictive, not purely obstructive as seen in COPD or occupational asthma.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.