In a 69-year-old man with chronic kidney disease and hypertension who has had 7 weeks of progressive mid‑thoracic back pain worse at night, radiation to the umbilicus, sensory loss at the T10 dermatome, anemia, hypercalcemia, hypoalbuminemia, and a positive straight‑leg raise, what is the most likely cause of his condition?

Neoplastic Epidural Spinal Cord Compression from Multiple Myeloma

The most likely diagnosis is neoplastic epidural spinal cord compression (answer a), almost certainly from multiple myeloma given the constellation of anemia, hypercalcemia, renal dysfunction, and progressive thoracic back pain with neurologic findings in an elderly patient. 1

Clinical Reasoning

This patient presents with multiple red flags that strongly suggest malignancy rather than benign causes:

Key Diagnostic Features Supporting Malignancy

Laboratory abnormalities form a classic triad for multiple myeloma:

• Anemia (hemoglobin 8 g/dL, hematocrit 25%) - severe normocytic anemia is characteristic of plasma cell disorders 1
• Hypercalcemia (corrected calcium approximately 11.5 mg/dL when adjusted for albumin 3.0 g/dL) - a hallmark of myeloma bone disease 1
• Renal dysfunction (creatinine 2.10, eGFR 34, BUN 42) - consistent with myeloma kidney or cast nephropathy 1
• Hypoalbuminemia (3.0 g/dL) - suggests chronic disease and possible monoclonal protein production 1

Clinical presentation strongly favors neoplastic compression:

• Progressive pain over 7 weeks worsening to severe intensity - the subacute progressive course is typical of metastatic disease 1
• Night pain - a classic red flag for malignancy in thoracic back pain 1
• Radicular pattern to umbilicus with T10 sensory loss - indicates nerve root involvement from epidural compression 1
• Bilateral positive straight leg raise - suggests significant spinal canal compromise 1
• Age 69 years - peak incidence for multiple myeloma is 65-70 years 1
• Generalized malaise and shoulder/hip pain - may represent additional skeletal involvement 1

Why Other Diagnoses Are Less Likely

Spinal epidural abscess (answer b) is unlikely because:

• No fever or systemic signs of infection
• Subacute 7-week course is too prolonged for typical bacterial abscess
• Laboratory findings (hypercalcemia, severe anemia) don't fit infectious etiology 1

Vertebral discitis (answer c) is unlikely because:

• Lacks fever and elevated inflammatory markers typically seen in discitis
• The constellation of hypercalcemia and severe anemia points away from infection
• No mention of elevated white blood cell count 1

Degenerative disc disease (answer d) is unlikely because:

• Doesn't explain the severe anemia, hypercalcemia, or renal dysfunction
• Night pain and progressive neurologic deficits are atypical for degenerative disease
• The ACR guidelines note that thoracic disc herniations are more common in younger patients (third to fifth decades) and often associated with trauma 1
• Degenerative disease wouldn't cause the systemic laboratory abnormalities present 1

Immediate Management Approach

Urgent MRI of the thoracic spine without and with IV contrast is the imaging modality of choice to confirm epidural spinal cord compression and assess the extent of vertebral involvement 1. The ACR Appropriateness Criteria designate MRI as "usually appropriate" for thoracic back pain with myelopathy or radiculopathy, specifically noting that thoracic myelopathy can be due to neoplastic etiologies 1.

Additional diagnostic workup should include:

• Serum protein electrophoresis (SPEP) and urine protein electrophoresis (UPEP) to identify monoclonal protein 1
• Serum free light chain assay 1
• Complete skeletal survey or whole-body low-dose CT to assess for lytic lesions 1
• Bone marrow biopsy if myeloma is confirmed 1

This patient requires emergent neurosurgical and oncology consultation given the presence of neurologic deficits (sensory loss at T10) and progressive symptoms, as epidural spinal cord compression from myeloma can lead to irreversible paralysis if not treated urgently 1.