A 56-year-old machinist with 22 years of exposure to beryllium-copper alloy presents with progressive exertional dyspnea, non-productive cough, and bibasilar crackles. Chest CT shows diffuse parenchymal nodules, reticulation, and honeycombing. Beryllium lymphocyte proliferation test (BeLPT) is markedly positive. Pulmonary function testing reveals FEV1 2.10 L (62% predicted), FVC 2.55 L (60% predicted), FEV1/FVC ratio 0.82 (preserved), TLC 4.20 L (62% predicted), and DLCO 11.8 mL/min/mmHg (40% predicted). The flow-volume loop is miniaturized with preserved peak expiratory flow and sharp descending limb. The pattern marked **A** in the diagram represents which of the following pulmonary function abnormalities?

Question

Accepted Answer

A. Restrictive pattern with reduced TLC and markedly reduced DLCO, with preserved FEV1/FVC ratio and miniaturized flow-volume loop. ## Why option 1 is correct

The pulmonary function pattern marked **A** in chronic beryllium disease (CBD) is a **restrictive pattern with reduced TLC and markedly reduced DLCO**. The case demonstrates the classic CBD physiology: proportional reduction in all lung volumes (TLC 62% predicted, VC 60% predicted, FRC 66% predicted, RV 72% predicted) with a preserved FEV1/FVC ratio (0.82), indicating no airway obstruction. The miniaturized flow-volume loop with preserved peak expiratory flow and sharp descending limb is pathognomonic for restriction. Most critically, DLCO is markedly reduced at 40% predicted—reflecting the alveolar-capillary inflammation and granulomatous infiltration characteristic of CBD. This pattern is indistinguishable from sarcoidosis on PFT alone and requires occupational history and positive BeLPT for diagnosis (Mayer AS, Hamzeh N, Maier LA. Semin Respir Crit Care Med. 2014;35(3):316-329).

## Why each distractor is wrong

- **Option 2 (Obstructive pattern)**: This patient has a preserved FEV1/FVC ratio (0.82), ruling out obstruction. Bronchodilator testing showed no response, confirming the absence of reversible airway disease. Obstructive patterns are not typical of CBD.

- **Option 3 (Mixed pattern with elevated RV/TLC)**: While RV is mildly elevated at 72% predicted, the RV/TLC ratio is not elevated (RV 1.65 L / TLC 4.20 L ≈ 0.39, normal), and there is no FEV1/FVC reduction. This pattern would suggest emphysema or asthma with air trapping, neither of which applies here.

- **Option 4 (Normal spirometry with isolated DLCO reduction)**: Although DLCO is isolated in some restrictive diseases, this patient has clear spirometric restriction (FVC 60% predicted, TLC 62% predicted). Isolated DLCO reduction without TLC reduction would suggest early interstitial lung disease or pulmonary hypertension, not established CBD with granulomatous disease.

**High-Yield:** CBD presents with a **restrictive PFT pattern (reduced TLC, preserved FEV1/FVC) and markedly reduced DLCO**—identical to sarcoidosis; distinguish by occupational exposure history and positive BeLPT.

[cite: Mayer AS, Hamzeh N, Maier LA. Sarcoidosis and chronic beryllium disease: similarities and differences. Semin Respir Crit Care Med. 2014;35(3):316-329.]

Answer

B. Mixed obstructive-restrictive pattern with reduced FEV1/FVC ratio and elevated RV/TLC ratio

Answer

C. Normal spirometry with isolated DLCO reduction and normal lung volumes

Answer

D. Obstructive pattern with reduced FEV1/FVC ratio and air trapping, responsive to bronchodilators

Explanation

Why option 1 is correct

Why each distractor is wrong

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