A 27-year-old woman is brought to the emergency department due to a 2-day history of progr… — USMLE Step 2 CK

A 27-year-old woman is brought to the emergency department due to a 2-day history of progressively worsening shortness of breath, fever, and coughing up blood-tinged sputum. She has a history of systemic lupus erythematosus (SLE) complicated by class IV lupus nephritis, for which she takes mycophenolate mofetil and low-dose prednisone. Her temperature is $38.8^\circ\text{C}$ ( $101.8^\circ\text{F}$ ), blood pressure is $105/65\text{ mmHg}$ , pulse is $124/\text{min}$ , and respirations are $28/\text{min}$ . Oxygen saturation is $86\%$ on room air. Physical examination reveals a pale, fatigued woman in moderate respiratory distress. Auscultation of the lungs reveals diffuse bilateral crackles. There is no jugular venous distension. Cardiac examination shows a regular tachycardia with no murmurs, rubs, or gallops. Trace bilateral pedal edema is present.

Laboratory results:

Laboratory Test	Result	Reference Range
Hemoglobin	$7.2\text{ g/dL}$ (Baseline: $11.5\text{ g/dL}$ )	$12.0 - 16.0\text{ g/dL}$
Leukocyte count	$5,400/\text{mm}^3$	$4,500 - 11,000/\text{mm}^3$
Platelet count	$140,000/\text{mm}^3$	$150,000 - 400,000/\text{mm}^3$
Blood urea nitrogen	$48\text{ mg/dL}$	$7 - 18\text{ mg/dL}$
Serum creatinine	$2.3\text{ mg/dL}$ (Baseline: $1.4\text{ mg/dL}$ )	$0.6 - 1.2\text{ mg/dL}$

Arterial blood gas (room air):

Parameter	Result
pH	$7.50$
pCO $_2$	$26\text{ mmHg}$
pO $_2$	$54\text{ mmHg}$
HCO $_3^-$	$20\text{ mEq/L}$

Chest radiograph reveals new diffuse, bilateral patchy alveolar infiltrates. An emergency bedside echocardiogram demonstrates a left ventricular ejection fraction of $60\%$ with normal right ventricular function and no significant valvular abnormalities.

Which of the following diagnostic findings would most likely be seen on further evaluation of this patient?

Progressively bloodier return on sequential aliquots of bronchoalveolar lavage fluidAnswer
B
Elevated pulmonary capillary wedge pressure on right heart catheterization
C
Abundant neutrophils containing intracellular gram-positive diplococci on sputum Gram stain
D
Multiple segmental perfusion defects on ventilation-perfusion scintigraphy
E
Expected arterial partial pressure of carbon dioxide of 38 mmHg calculated via Winter formula

Answer

Progressively bloodier return on sequential aliquots of bronchoalveolar lavage fluid

Diffuse alveolar hemorrhage (DAH) is a rare but life-threatening complication of systemic lupus erythematosus (SLE), particularly in patients with active lupus nephritis. The classic presentation includes dyspnea, fever, hemoptysis, and new bilateral alveolar infiltrates. The critical distinguishing feature in this vignette is the acute, profound drop in hemoglobin (from 11.5 to 7.2 g/dL), which indicates massive blood loss. Given the absence of gastrointestinal or other external bleeding, this internal blood loss must be localized to the pulmonary parenchyma. The gold standard for diagnosing DAH is bronchoscopy with bronchoalveolar lavage (BAL). In DAH, sequential aliquots of BAL fluid become progressively bloodier, confirming active alveolar bleeding rather than localized airway trauma from the procedure. Prompt recognition is critical as treatment requires high-dose corticosteroids and immunosuppressive therapy.

Step-by-Step Solution

Analyze the patient's vital signs and physical examination.

The patient is hypoxic, tachypneic, and tachycardic with bilateral lung crackles, indicating an acute pulmonary process.

To establish the primary organ system involved in the acute decompensation.

Evaluate the laboratory data and imaging.

Chest radiograph shows diffuse bilateral infiltrates. Labs reveal an acute drop in hemoglobin by 4.3 g/dL without signs of external bleeding. Echocardiogram is normal.

To differentiate between infectious, cardiogenic, and hemorrhagic causes of pulmonary infiltrates.

Synthesize the findings with the patient's medical history.

A patient with active SLE (lupus nephritis) presenting with new pulmonary infiltrates, hemoptysis, and massive unexplained anemia is highly suspicious for diffuse alveolar hemorrhage (DAH).

To formulate the most likely diagnosis based on the clinical triad.

Identify the diagnostic gold standard for the suspected condition.

Bronchoscopy with bronchoalveolar lavage (BAL) showing progressively bloody aliquots confirms DAH.

To answer the specific question asked in the stem regarding further evaluation findings.

Key Concept

Diffuse alveolar hemorrhage in systemic lupus erythematosus is characterized by the triad of hemoptysis, diffuse pulmonary infiltrates, and an acute drop in hemoglobin. Bronchoscopy with serial bronchoalveolar lavage confirms the diagnosis.

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