A 43-year-old woman is brought to the emergency department due to a 3-day history of escal… — USMLE Step 2 CK

A 43-year-old woman is brought to the emergency department due to a 3-day history of escalating, throbbing headaches, blurred vision, and severe shortness of breath. The patient has a known 4-year history of diffuse cutaneous systemic sclerosis. Three weeks ago, she received a high-dose oral prednisone taper for an exacerbation of joint pain and severe skin tightness.

Upon arrival, her temperature is $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ ), blood pressure is $230/125 \text{ mmHg}$ , heart rate is $115/\text{min}$ , and respiratory rate is $26/\text{min}$ with an oxygen saturation of $91\%$ on room air. Physical examination reveals extensive skin thickening over the face, trunk, and proximal upper extremities. Fundoscopic examination demonstrates bilateral flame-shaped hemorrhages and papilledema. Chest auscultation reveals bibasilar crackles.

Laboratory studies are as follows:

Test	Result	Reference Range
Hemoglobin	$8.2 \text{ g/dL}$	$12.0-16.0 \text{ g/dL}$
Platelets	$78,000/\text{mm}^3$	$150,000-400,000/\text{mm}^3$
Blood urea nitrogen	$52 \text{ mg/dL}$	$7-18 \text{ mg/dL}$
Serum creatinine	$3.4 \text{ mg/dL}$	$0.6-1.2 \text{ mg/dL}$
Thyroid-stimulating hormone (TSH)	$0.2 \mu\text{U/mL}$	$0.4-4.0 \mu\text{U/mL}$
Free thyroxine (T4)	$1.2 \text{ ng/dL}$	$0.9-1.7 \text{ ng/dL}$

Peripheral blood smear shows 4 to 6 schistocytes per high-power field.

Arterial blood gas on room air:
pH: $7.32$
$\text{PaCO}_2$ : $30 \text{ mmHg}$
$\text{PaO}_2$ : $60 \text{ mmHg}$
Bicarbonate: $15 \text{ mEq/L}$

Urinalysis reveals $1+$ proteinuria with no red blood cell casts. A recent outpatient sputum culture grew only normal respiratory flora.

Which of the following is the most appropriate next step in the management of this patient's current condition?

Administer oral captoprilAnswer
B
Administer intravenous furosemide and noninvasive positive-pressure ventilation
C
Administer an intravenous sodium bicarbonate infusion
D
Initiate empiric intravenous broad-spectrum antimicrobial therapy
E
Administer intravenous levothyroxine

Answer

Administer oral captopril

The correct step is to administer oral captopril. This patient is presenting with scleroderma renal crisis (SRC), a life-threatening complication of systemic sclerosis characterized by malignant hypertension (evidenced by papilledema and flame-shaped hemorrhages) and rapidly progressive oliguric acute kidney injury. The recent use of high-dose corticosteroids is a classic precipitating trigger for SRC. The pathogenesis involves intense activation of the renin-angiotensin-aldosterone system (RAAS) due to renal vascular injury. Therefore, short-acting ACE inhibitors, specifically captopril, are the first-line treatment and must be initiated immediately and titrated rapidly, even in the setting of acute kidney injury. SRC can also cause microangiopathic hemolytic anemia (schistocytes, thrombocytopenia) due to endothelial damage, which may mimic thrombotic thrombocytopenic purpura, but it resolves with aggressive ACE inhibitor therapy.

Step-by-Step Solution

Analyze the patient's presentation and medical history.

The patient has diffuse cutaneous systemic sclerosis and presents with new-onset malignant hypertension, microangiopathic hemolytic anemia, and acute kidney injury following high-dose corticosteroid use.

To identify the primary acute pathophysiologic process.

Diagnose the acute condition.

The clinical picture is classic for Scleroderma Renal Crisis (SRC).

Recognizing SRC is critical because its management diverges significantly from typical hypertensive emergencies.

Evaluate the laboratory and arterial blood gas findings.

The ABG shows a fully compensated metabolic acidosis (Winter's formula matches actual PaCO2). The thyroid panel shows euthyroid sick syndrome.

To rule out secondary superimposed complications that would require separate, potentially contraindicated treatments.

Determine the appropriate pharmacologic intervention.

Select a short-acting ACE inhibitor (captopril).

ACE inhibitors specifically target and break the cycle of malignant renin-angiotensin-aldosterone system (RAAS) activation that drives SRC.

Key Concept

Scleroderma Renal Crisis (SRC) presents with malignant hypertension, acute kidney injury, and often microangiopathic hemolytic anemia. It is frequently triggered by glucocorticoid use in patients with systemic sclerosis. Prompt initiation of a short-acting ACE inhibitor (e.g., captopril) is mandatory, even in the setting of renal failure.

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