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Difficulty: HardFormulating a Differential Diagnosis

A 4848-year-old woman comes to the pulmonology clinic due to progressive shortness of breath over the past 44 months. Initially, she noticed breathlessness only when climbing stairs, but she now feels short of breath after walking a single block on level ground. She has a medical history of severe gastroesophageal reflux disease and Raynaud phenomenon, for which she takes omeprazole and amlodipine. She has never smoked. Her blood pressure is 115/72115/72 mmHg, pulse is 8686/min, and respirations are 1818/min. Pulse oximetry is 96%96\% on room air at rest, but drops to 89%89\% during a 66-minute walk test.

Physical examination reveals tight, thickened skin over her fingers and face, with several small, dilated blood vessels visible on her cheeks. Auscultation of the lungs is clear bilaterally. Cardiovascular examination reveals a prominently split second heart sound with a loud pulmonary component, and a holosystolic murmur at the left lower sternal border that becomes louder with inspiration. There is trace bilateral lower extremity edema.

Laboratory evaluation shows a positive antinuclear antibody (ANA) titer at 1:6401:640 with a centromere pattern.

Pulmonary function tests (PFTs) are performed with the following results:

ParameterPatient's ValueNormal Reference
FVC92%92\% of predicted≥80%\geq 80\%
FEV190%90\% of predicted≥80%\geq 80\%
FEV1/FVC82%82\%≥70%\geq 70\%
TLC90%90\% of predicted80%−120%80\% - 120\%
DLCO38%38\% of predicted≥80%\geq 80\%

Based on the patient's presentation and diagnostic findings, which of the following is the most likely diagnosis?

  1. Pulmonary arterial hypertensionAnswer
  2. B
    Interstitial lung disease
  3. C
    Heart failure with preserved ejection fraction
  4. D
    Chronic thromboembolic pulmonary hypertension
  5. E
    Recurrent microaspiration pneumonitis

Answer

Pulmonary arterial hypertension
The correct answer is pulmonary arterial hypertension. This patient's clinical presentation is classic for limited cutaneous systemic sclerosis (lcSSc), also known as CREST syndrome (Calcinosis cutis, Raynaud phenomenon, Esophageal dysmotility, Sclerodactyly, Telangiectasia). Patients with lcSSc are at a significantly increased risk for developing pulmonary arterial hypertension (PAH), a form of Group 1 pulmonary hypertension. PAH presents with progressive exertional dyspnea, and physical examination often reveals signs of right ventricular pressure overload and right heart failure, such as a loud pulmonic component of the second heart sound (P2), a tricuspid regurgitation murmur (holosystolic, louder with inspiration), and peripheral edema. Crucially, PFTs in PAH demonstrate an isolated, significant reduction in DLCO with normal spirometry (normal FVC, normal FEV1/FVC) and normal lung volumes (normal TLC). This isolated gas exchange defect differentiates PAH from parenchymal lung diseases.

Step-by-Step Solution

1
Identify the underlying systemic condition.
The patient has limited cutaneous systemic sclerosis (CREST syndrome).
This is evidenced by her history of Raynaud phenomenon, GERD, sclerodactyly (tight skin on fingers), telangiectasias, and a positive anti-centromere ANA.
2
Localize the cause of dyspnea and physical exam findings.
The exertional dyspnea, clear lungs, loud P2, and holosystolic murmur (tricuspid regurgitation) indicate right ventricular pressure overload and pulmonary hypertension.
These signs point away from left-sided heart failure and suggest a primary pulmonary vascular or parenchymal etiology.
3
Interpret the pulmonary function tests.
The PFTs show an isolated, severe reduction in DLCO (38%38\%).
Normal FVC, FEV1/FVC, and TLC rule out significant obstructive or restrictive (parenchymal) lung disease. The isolated low DLCO indicates a gas exchange defect at the alveolar-capillary membrane, characteristic of pulmonary vascular disease.
4
Synthesize findings to formulate the diagnosis.
The combination of limited cutaneous systemic sclerosis and isolated pulmonary vascular disease strongly points to pulmonary arterial hypertension.
Pulmonary arterial hypertension (WHO Group 1) is a well-known, severe complication of limited cutaneous systemic sclerosis that matches all the clinical and laboratory data.

Key Concept

Pulmonary arterial hypertension is a major complication of limited cutaneous systemic sclerosis (CREST syndrome) and typically presents with right heart failure signs and an isolated reduction in DLCO on pulmonary function testing.
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Topics

Formulating a Differential Diagnosis

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