Hypercalcemia Due to Immobilization

Abstract

Background: Hypercalcemia associated with immobilization is an infrequent diagnosis. It is usually associated with prolonged immobility due to traumatic brain injury or spinal cord injuries. It results from rapid bone turnover. Diagnosis requires workup to rule out other causes of hypercalcemia. Keywords: Hypercalcemia; immobilizationCASE REPORT: We report a case of a 49 year old woman with severe traumatic brain injury and paraplegia following an electric-scooter accident. She had an extended stay in hospital and was noted to be hypercalcemic after six months’ in-patient. Laboratory investigations showed increased calcium level at 3.34 mmol/l (ref. 2.15–2.50 mmol/l) with diminished parathyroid hormone (PTH) level of 0.2 pmol/l (ref. 1.6–6.9 pmol/l), low 25-hydroxyvitamin D at 26.7 ug/l (toxicity >100 ug/l) and low 1,25-dihydroxyvitamin D at 13 pg/l (ref. 18–78 pg/l) with increased 24-H urinary calcium at 11.74 mmol/day (ref. 2.50 – 7.50 mmol/day). There was no clinical or biochemical evidence of other endocrinopathies such as hyperthyroidism or adrenal insufficiency. There was also no underlying malignancy to explain the hypercalcemia. In the context of recent prolonged immobility, a diagnosis of immobilisation hypercalcemia (IH) was made. The pathophysiology of IH is unclear. It is said that muscle activity transmits signal for bone formation through osteocytes and with immobility, mechanical stimulation is reduced, causing unopposed resorption. Another cause may be increased acidic environment due to low blood flow which impairs bone mineralization. There is also increased osteoclastic resorption, leading to loss of calcium from bones and hypercalciuria. Hypercalcemia occurs when calcium efflux from bone exceeds renal calcium excretion. For our patient, hydration therapy was initiated with no improvement in calcium. SC calcitonin was added and IV pamidronate given. Two weeks after treatment serum calcium improved to 2.38 mmol/L and remained normal on subsequent monitoring. Conclusion: IH is a known but uncommonly recognized complication in immobile patients. If not treated properly patients may develop typical complications of hypercalcemia including dehydration, confusion and renal impairment. Mobilization by using weight bearing exercises where possible is a cornerstone of long term management. In conclusion, our case serves as an important reminder of this differential and illustrates the management of IH.