A 28 years old woman having limited cutaneous scleroderma for the last 10 years complains of shoness of breath for last one month. Her pulmonary function tests (PFT) are a following: PFT Observed Predicted FVC 2.63 2.82 FEV1 88% 80% DLCO 5.26 16.3 Which of the following is the most probable diagnosis in this patient?

**Core Concept**
The patient's presentation of shortness of breath and limited cutaneous scleroderma suggests an involvement of the pulmonary system, specifically a restrictive lung disease due to interstitial fibrosis.

**Why the Correct Answer is Right**
The observed values in the pulmonary function tests (PFT) show a decreased Forced Vital Capacity (FVC) and a decreased Diffusing Capacity of the Lung for Carbon Monoxide (DLCO), while the Forced Expiratory Volume in one second (FEV1) is preserved. This pattern is indicative of restrictive lung disease, which is a hallmark of interstitial lung disease (ILD) in scleroderma patients. The significant decrease in DLCO suggests a severe impairment in gas exchange, consistent with the presence of fibrosis in the lung parenchyma.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not directly related to the patient's presentation and the PFT results.
**Option B:** This option does not explain the significant decrease in DLCO, which is a key feature in this patient's PFT results.
**Option C:** This option does not account for the patient's 10-year history of limited cutaneous scleroderma and its known association with ILD.

**Clinical Pearl / High-Yield Fact**
In patients with scleroderma, early detection and treatment of interstitial lung disease (ILD) are crucial to prevent progression and improve lung function. A high index of suspicion should be maintained, especially in those with limited cutaneous disease, as they are at increased risk of developing ILD.

**Correct Answer: C. Pulmonary fibrosis, a complication of scleroderma.**

✓ Correct Answer: A. Interstitial lung disease