Weight loss and back pain in a 68-year-old man on long-term steroids
A 68-year-old man presents with 6 weeks of progressive mid-thoracic back pain, worse at night and unrelieved by rest. He has lost 5 kg unintentionally. He has chronic obstructive pulmonary disease and has taken prednisolone 15 mg daily for 4 years for presumed polymyalgia rheumatica. He also has type 2 diabetes. Examination shows thoracic kyphosis, tenderness over T7-T8, and no neurological deficit. Laboratory tests: ESR 55 mm/h, CRP 30 mg/L, calcium corrected 2.72 mmol/L (10.9 mg/dL), alkaline phosphatase 210 U/L (raised), albumin 32 g/L, total protein 84 g/L. Radiograph shows a wedge compression fracture at T7 with generalised osteopenia.
1. List your differential diagnosis for the vertebral fracture and hypercalcaemia, and explain how you would distinguish between them.
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The combination of a vertebral compression fracture, hypercalcaemia, raised alkaline phosphatase, weight loss and night pain in a patient on long-term glucocorticoids demands that malignancy be excluded before attributing everything to osteoporosis.
Differential:
- Glucocorticoid-induced osteoporosis - expected with 4 years of prednisolone 15 mg; fractures can occur at relatively preserved BMD. However, isolated hypercalcaemia is not typical unless the patient is immobilised.
- Multiple myeloma - classic for back pain, anaemia, hypercalcaemia, renal impairment and lytic lesions; a compression fracture may be the presenting feature. Check serum protein electrophoresis, free light chains, urinary Bence Jones protein, and a skeletal survey or whole-body MRI.
- Metastatic malignancy (lung, prostate, breast, kidney, thyroid) - hypercalcaemia via PTHrP or osteolysis; check PSA in men, chest imaging, and imaging of the spine.
- Primary hyperparathyroidism - hypercalcaemia with raised or inappropriately normal PTH; less likely to cause night pain and weight loss.
- Osteomalacia - low calcium and phosphate, raised ALP; not hypercalcaemia.
- Paget's disease - raised ALP, but usually focal and not hypercalcaemic unless immobilised.
Distinguishing tests: serum PTH, PTHrP, vitamin D, protein electrophoresis and free light chains, PSA, full blood count, renal function, and MRI of the whole spine (to assess cord compression and marrow infiltration). A bone scan or PET-CT may be needed.
2. What is the immediate priority in management, and how should his long-term bone health be addressed?
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Immediate priority: exclude spinal cord compression and unstable fracture. Ask about leg weakness, sensory level, and bladder or bowel dysfunction; if any are present, arrange emergency MRI of the whole spine and involve spinal surgery and oncology. Otherwise, urgent MRI within days is still warranted given night pain, weight loss and hypercalcaemia.
Hypercalcaemia management: correct with intravenous 0.9% saline, then consider a single dose of intravenous zoledronic acid (caution with renal function) or pamidronate once malignancy is being addressed; monitor calcium and renal function. Avoid thiazides and immobilisation.
Long-term bone health:
- Review the glucocorticoid dose - question whether the PMR diagnosis is correct and whether 15 mg daily for 4 years is justified; aim for the lowest effective dose and consider steroid-sparing agents.
- Calcium and vitamin D supplementation (e.g. calcium 1000 mg and vitamin D 800-1000 IU daily), with dietary assessment.
- Bone protection: a bisphosphonate (alendronate or risedronate) or zoledronic acid is first-line for glucocorticoid-induced osteoporosis in a patient with a fragility fracture; denosumab or teriparatide are alternatives for severe or refractory cases. Check dental health before bisphosphonates.
- Falls prevention, weight-bearing exercise as tolerated, smoking cessation, and diabetes control.
- DXA scan and repeat imaging to monitor; consider vertebral augmentation only for refractory pain.
- In men, check testosterone and treat hypogonadism if present.