What is the differential diagnosis (Ddx) for an adult patient with no prior medical history presenting with pulmonary edema and leg paralysis?

Differential Diagnosis for Pulmonary Edema with Leg Paralysis

In an adult with no prior medical history presenting with pulmonary edema and leg paralysis, the most critical diagnosis to consider is acute pulmonary embolism (PE) with concurrent deep vein thrombosis (DVT) causing lower limb paralysis from neurologic complications, followed by systemic sclerosis with pulmonary veno-occlusive disease (SSc-PVOD), and cardiac causes including acute myocardial infarction with cardiogenic shock. 1, 2

Primary Differential Diagnoses

1. Pulmonary Embolism with Neurologic Complications

• Lower limb paralysis is a recognized risk factor for VTE with an odds ratio of 6.08 for history of VTE, and current lower limb paralysis is specifically included in the IMPROVE risk assessment model for VTE 1
• PE presents with acute onset dyspnea, chest pain, and hemoptysis, with ECG signs of right ventricular overload 1
• Unilateral leg swelling combined with unexplained hypoxemia (SaO₂ <95%) places patients in the "unsafe" category with 42.1% probability of PE 1
• Pulmonary edema can occur as a manifestation of right heart failure from massive PE 1
• The combination of leg paralysis (suggesting DVT with neurologic sequelae) and pulmonary edema (from PE-induced right heart failure) makes this a life-threatening presentation requiring immediate evaluation 1

2. Systemic Sclerosis with Pulmonary Veno-Occlusive Disease

• SSc-PVOD presents with severe pulmonary hypertension, pulmonary edema, and digital ulceration with potential peripheral neuropathy 2
• Pulmonary edema occurs from intimal proliferation and fibrosis of intrapulmonary veins causing hydrostatic pulmonary edema 2
• Pleural effusions and interlobular septal thickening on CT imaging support PVOD 2
• Critical pitfall: Pulmonary vasodilators worsen pulmonary edema in SSc-PVOD patients and must be avoided 2

3. Acute Myocardial Infarction with Cardiogenic Shock

• Acute MI is a precipitating factor in 15% of pulmonary edema cases and is associated with increased in-hospital mortality 3
• Cardiogenic shock presents with systolic BP <90 mmHg, tissue hypoperfusion, and pulmonary congestion developing rapidly 1
• Leg paralysis could represent peripheral hypoperfusion from shock state 1
• Type 2 MI from supply-demand mismatch can occur with relative hypotension in the setting of acute illness 1

4. Acute Spinal Cord Injury with Neurogenic Pulmonary Edema

• Acute spinal cord injury or paralysis (<1 month) is a recognized thrombotic risk factor 1
• Neurogenic pulmonary edema can develop from massive sympathetic discharge following acute spinal cord injury 4
• This represents permeability edema rather than hydrostatic edema 4

5. Hypertensive Heart Failure with Acute Neurologic Event

• Hypertensive HF presents with high BP, pulmonary congestion, and relatively preserved LV systolic function 1
• Patients may be euvolemic or only mildly hypervolemic with signs of pulmonary congestion without systemic congestion 1
• High blood pressure is the most common precipitating factor (29%) for pulmonary edema 3
• Concurrent stroke could explain leg paralysis 1

Critical Diagnostic Approach

Immediate Assessment

1. Evaluate hemodynamic stability: Check for shock index (HR/SBP >1.0), systolic BP <90 mmHg, altered mental status, or signs of tissue hypoperfusion 1
2. Assess oxygenation: Unexplained hypoxemia (SaO₂ <95%) without prior lung disease suggests PE 1
3. Examine legs: Look for unilateral leg swelling (DVT), bilateral edema (systemic cause), or complete paralysis (neurologic injury) 1

Essential Diagnostic Tests

• ECG: Look for signs of right ventricular overload (PE), acute MI, or ischemia 1
• Chest radiograph: Bilateral pulmonary opacities with Kerley B lines and "batwing" appearance suggest hydrostatic edema; oligemia or amputation of hilar artery suggests PE 1, 5
• D-dimer: If pretest probability allows, negative D-dimer with ELISA (negative LR 0.07) can exclude PE in low-risk patients 1
• Troponin: Elevated troponin occurs in PE, acute MI, and Type 2 MI from supply-demand mismatch 1
• CT pulmonary angiography: Definitive test for PE if clinically indicated 1
• Echocardiography: Assess for right ventricular dysfunction (PE), left ventricular function (cardiogenic shock), and valvular disease 1, 2

Risk Stratification for PE

Using the Kline Rule, patients are "unsafe" for D-dimer testing if they have:

• Shock index >1.0 OR age >50 years PLUS any of: unexplained hypoxemia, unilateral leg swelling, recent major surgery, or hemoptysis 1
• These "unsafe" patients have 42.1% probability of PE and require immediate imaging 1

Common Pitfalls to Avoid

1. Never assume the leg paralysis is unrelated to the pulmonary edema—lower limb paralysis is a specific VTE risk factor and may indicate DVT with PE 1
2. Do not delay PE evaluation in hemodynamically unstable patients—massive PE can present with pulmonary edema from right heart failure 1
3. Avoid pulmonary vasodilators if PVOD is suspected—they worsen pulmonary edema in these patients 2
4. Do not overlook acute spinal cord injury—this can cause both leg paralysis and neurogenic pulmonary edema 1, 4
5. Consider cardiac causes even without chest pain—15% of pulmonary edema patients have acute MI at admission 3