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Difficulty: Very hardRheumatology and Immunology

A 48-year-old man is brought to the emergency department by his wife due to a 2-week history of worsening shortness of breath, fever, and coughing up blood-tinged sputum. He has a past medical history of chronic rhinosinusitis refractory to antibiotics, recurrent epistaxis, and bilateral knee pain over the past year. His only medication is ibuprofen as needed.

His temperature is 38.3∘C38.3^\circ\text{C} (100.9∘F100.9^\circ\text{F}), blood pressure is 155/95 mm Hg155/95\text{ mm Hg}, pulse is 112/min112/\text{min}, and respirations are 26/min26/\text{min}. Oxygen saturation is 89%89\% on room air.

Physical examination shows ulceration of the nasal septum and a saddle nose deformity. Lung auscultation reveals bilateral fine crackles. Heart sounds are normal. There is no peripheral edema.

Laboratory results are as follows:

TestResultReference Range
Leukocyte count14,500/mm314,500/\text{mm}^34,500−11,000/mm34,500-11,000/\text{mm}^3
Hemoglobin9.8 g/dL9.8\text{ g/dL}13.5−17.5 g/dL13.5-17.5\text{ g/dL}
Platelet count450,000/mm3450,000/\text{mm}^3150,000−400,000/mm3150,000-400,000/\text{mm}^3
Blood urea nitrogen52 mg/dL52\text{ mg/dL}8−20 mg/dL8-20\text{ mg/dL}
Serum creatinine3.1 mg/dL3.1\text{ mg/dL}0.7−1.3 mg/dL0.7-1.3\text{ mg/dL}
Thyroid-stimulating hormone (TSH)0.2 μU/mL0.2\ \mu\text{U/mL}0.4−4.0 μU/mL0.4-4.0\ \mu\text{U/mL}
Free T40.8 ng/dL0.8\text{ ng/dL}0.9−2.0 ng/dL0.9-2.0\text{ ng/dL}

Urinalysis shows 3+ protein and large blood; microscopy reveals 25-50 RBCs/hpf and occasional red blood cell casts.

An arterial blood gas on room air shows:
pH: 7.287.28
PaO 2_2: 58 mm Hg58\text{ mm Hg}
PaCO 2_2: 25 mm Hg25\text{ mm Hg}
HCO 3−_3^-: 11 mEq/L11\text{ mEq/L}

A chest X-ray shows multiple bilateral nodular opacities, several of which are cavitating.

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

  1. Administer intravenous methylprednisolone and obtain proteinase 3 antineutrophil cytoplasmic antibody levelsAnswer
  2. B
    Administer intravenous sodium bicarbonate and prepare for endotracheal intubation
  3. C
    Administer intravenous furosemide and initiate noninvasive positive pressure ventilation
  4. D
    Start empiric intravenous vancomycin and piperacillin-tazobactam
  5. E
    Initiate intravenous levothyroxine and obtain a thyroid ultrasound

Answer

The most appropriate next step is to administer intravenous methylprednisolone and obtain proteinase 3 antineutrophil cytoplasmic antibody levels.
The correct answer addresses the urgent need to suppress the severe autoimmune inflammation characteristic of Granulomatosis with polyangiitis (GPA). This patient presents with the classic triad of upper respiratory tract involvement (saddle nose deformity, nasal ulceration), lower respiratory tract involvement (cavitary lung nodules, hemoptysis), and focal necrotizing glomerulonephritis (acute kidney injury with RBC casts). This presentation represents a rapidly fatal pulmonary-renal syndrome. The most appropriate initial step is the immediate administration of high-dose systemic corticosteroids (such as intravenous methylprednisolone) to halt immune-mediated tissue destruction, concurrently with diagnostic serologic testing for c-ANCA (specifically proteinase 3 [PR3] antibodies).

Step-by-Step Solution

1
Analyze the clinical presentation.
The patient exhibits the classic triad of Granulomatosis with polyangiitis (GPA): upper respiratory tract involvement (nasal septal ulceration, saddle nose), lower respiratory tract involvement (cavitary lung nodules, hemoptysis), and focal necrotizing glomerulonephritis (acute kidney injury with RBC casts).
Recognizing this triad is crucial to diagnose GPA, a life-threatening pulmonary-renal syndrome.
2
Interpret the arterial blood gas using Winter's formula.
Expected PaCO2 = (1.5 × 11) + 8 = 24.5 ± 2. The measured PaCO2 of 25 mm Hg indicates perfect respiratory compensation for the metabolic acidosis.
To rule out a superimposed, uncompensated respiratory acidosis that would urgently require mechanical ventilation.
3
Evaluate the thyroid function tests.
Low TSH and low Free T4 in the setting of severe systemic illness indicates euthyroid sick syndrome (nonthyroidal illness syndrome).
To rule out true hypothyroidism and avoid unnecessary and potentially harmful thyroid hormone replacement.
4
Determine the optimal immediate management.
Initiate high-dose systemic corticosteroids (e.g., intravenous methylprednisolone) and order serologic testing for c-ANCA (PR3 antibodies).
Delaying immunosuppressive therapy in organ-threatening ANCA-associated vasculitis can lead to irreversible renal failure or fatal pulmonary hemorrhage.

Key Concept

Diagnosis and acute management of Granulomatosis with polyangiitis (GPA) presenting as a pulmonary-renal syndrome.
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Topics

Rheumatology and Immunology

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