A 68-year-old man is brought to the emergency department by his daughter due to worsening confusion, profound fatigue, and severe lower back pain over the past two weeks. He has a history of hypertension. Temperature is 37.1°C (98.8°F), blood pressure is 110/70 mmHg, pulse is 112/min, and respiratory rate is 16/min. Physical examination reveals dry mucous membranes and point tenderness over the L3 and L4 vertebrae. Neurologic examination shows no focal deficits, but the patient is lethargic and oriented only to name.
Laboratory studies show:
- Hemoglobin: 8.9 g/dL
- Platelet count: 140,000/mm³
- Leukocyte count: 4,500/mm³
- Serum calcium: 13.8 mg/dL
- Serum creatinine: 2.8 mg/dL (baseline 0.9 mg/dL)
- Blood urea nitrogen: 56 mg/dL
- Total protein: 10.2 g/dL
- Albumin: 3.1 g/dL
Arrange the following management and diagnostic steps in the most appropriate chronological sequence for this patient.
- 1Administer continuous intravenous hydration with isotonic saline
- 2Obtain serum protein electrophoresis, immunofixation, and free light chain assays
- 3Perform a whole-body low-dose computed tomography (CT) scan
- 4Perform a bone marrow aspiration and biopsy
- 5Initiate targeted induction chemotherapy (e.g., bortezomib, lenalidomide, dexamethasone)