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Difficulty: MediumRheumatology and Immunology

A woman, aged 48, is brought to the acute care clinic by her husband due to a 3-day history of worsening shortness of breath, severe headache, and blurry vision. She has known diagnoses of diffuse cutaneous systemic sclerosis and hypothyroidism, for which she takes mycophenolate mofetil and levothyroxine. Her temperature is 37.1°C (98.8°F), blood pressure is 225/115 mm Hg, heart rate is 108/min, and respiratory rate is 26/min. Oxygen saturation is 91% on ambient air. Physical examination reveals thickened, tight skin over the face, trunk, and proximal extremities. Funduscopic examination shows bilateral flame-shaped hemorrhages. Cardiopulmonary auscultation reveals bilateral basilar crackles and a loud S2S_2. There is 2+ pitting edema of the lower extremities.

Laboratory evaluations show:
- Hemoglobin: 8.4 g/dL
- Platelets: 85,000/mm 3^3
- Leukocytes: 11,500/mm 3^3
- Serum creatinine: 3.2 mg/dL (baseline was 0.9 mg/dL two months ago)
- Blood urea nitrogen: 48 mg/dL
- TSH: 2.5 μ\mu U/mL (Reference: 0.4-4.0 μ\mu U/mL)
- Free T4: 0.5 ng/dL (Reference: 0.9-1.7 ng/dL)
- Peripheral blood smear: 3-5 schistocytes per high-power field
- Arterial blood gas (ambient air): pH 7.32, pCO2pCO_2 30 mm Hg, pO2pO_2 65 mm Hg, HCO3−HCO_3^- 15 mEq/L

Which of the following interventions is the most appropriate next step in the management of this patient?

  1. A
    Administer inhaled albuterol and systemic glucocorticoids
  2. B
    Administer intravenous sodium bicarbonate for uncompensated metabolic acidosis
  3. Initiate oral captopril therapyAnswer
  4. D
    Initiate intravenous vancomycin and piperacillin-tazobactam
  5. E
    Increase the levothyroxine dose for presumed primary hypothyroidism

Answer

Initiate oral captopril therapy
The patient's presentation of malignant hypertension, acute kidney injury, and microangiopathic hemolytic anemia in the setting of diffuse cutaneous systemic sclerosis is highly characteristic of scleroderma renal crisis (SRC). SRC is precipitated by renal vascular injury leading to severe ischemia and a massive surge in renin production. The first-line, life-saving treatment is the rapid initiation of an angiotensin-converting enzyme (ACE) inhibitor, typically captopril, to directly counteract the renin-angiotensin-aldosterone system (RAAS) hyperactivation. Even in the presence of acute kidney injury, ACE inhibitors must be started and titrated to control blood pressure.

Step-by-Step Solution

1
Identify the primary clinical syndrome based on the patient's history and presentation.
The patient has systemic sclerosis and presents with new-onset malignant hypertension, acute kidney injury, and microangiopathic hemolytic anemia (schistocytes, thrombocytopenia).
This triad of findings in a patient with diffuse cutaneous systemic sclerosis establishes the diagnosis of scleroderma renal crisis (SRC).
2
Determine the underlying pathophysiology driving the acute crisis.
SRC is caused by intimal thickening of the renal arterioles leading to severe renal ischemia. This ischemia triggers massive activation of the renin-angiotensin-aldosterone system (RAAS).
Understanding that RAAS hyperactivation is the primary driver of the malignant hypertension is essential for selecting targeted pharmacotherapy.
3
Select the most appropriate evidence-based intervention.
An angiotensin-converting enzyme (ACE) inhibitor, such as short-acting captopril, must be initiated immediately.
ACE inhibitors directly block the RAAS cascade, reversing the primary pathophysiologic mechanism of SRC. They are life-saving and should be used even in the setting of acute kidney injury.

Key Concept

Scleroderma renal crisis presents with malignant hypertension, acute kidney injury, and microangiopathic hemolytic anemia. It is a life-threatening emergency that must be treated immediately with an ACE inhibitor (e.g., captopril) to reverse massive RAAS activation.
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Topics

Rheumatology and Immunology

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