Question

A patient presents with breathlessness. He has bilateral basal crepitations. Lung function tests reveal a decrease in total lung capacity (TLC) and vital capacity (VC), with a normal FEV₁/VC ratio. The most likely diagnosis is

• A. Chronic bronchitis
• B. Idiopathic pulmonary fibrosis
• C. Cystic fibrosis
• D. Allergic bronchopulmonary aspergillosis

Hint:

A fall in TLC and VC with a normal FEV1/VC ratio means restrictive, not obstructive, lung disease.

Answer 1

The Correct Option is B

Step 1: Classify the lung function pattern.
Lung diseases are broadly grouped as obstructive or restrictive. In obstructive disease, airflow out of the lung is blocked, so the FEV1/VC ratio falls. In restrictive disease, the lung cannot expand fully, so both TLC and VC fall together while the FEV1/VC ratio stays normal or even rises slightly.

Step 2: Apply this to the given values.
Here both TLC and VC are reduced, and the FEV1/VC ratio is normal. This is a textbook restrictive pattern, not an obstructive one.

Step 3: Match the pattern to the clinical picture.
Bilateral basal crepitations with a restrictive pattern is the classic combination for idiopathic pulmonary fibrosis, where scarring stiffens the lung tissue, mostly at the bases, and pulls the lung volumes down without blocking the airways.

Step 4: Rule out the other options.
Chronic bronchitis (A) is an obstructive disease, so FEV1/VC would fall, not stay normal. Cystic fibrosis (C) causes chronic airway obstruction and recurrent infection with an obstructive picture. Allergic bronchopulmonary aspergillosis (D) is a hypersensitivity reaction in asthmatic or cystic fibrosis airways, again producing obstruction, not restriction. None of these three fit a pure restrictive picture with basal crepitations.

Step 5: Final answer.
\[ \boxed{\text{Idiopathic pulmonary fibrosis}} \]