Hyperphosphatemia in a patient with spinal cord injury who received etidronate for the treatment of heterotopic ossification.

INTRODUCTION: Heterotopic ossification (HO) is defined as ectopic bone formation around peripheral joints and in soft tissues. HO is a common complication of diseases of the central nervous system, such as spinal cord injury (SCI) and traumatic brain injury. HO is seen in up to 50% of patients with SCI and typically occurs in the first 12 weeks after onset of injury. Although no treatment method is proven to be curative, nonsteroidal anti-inflammatory drugs, irradiation of the involved body part and bisphosphonates are commonly used in the management of HO.

CASE PRESENTATION: Here we present a 27-year-old male patient with a T10 ASIA Impairment Scale (AIS) A SCI, who developed hyperphosphatemia as a complication of bisphosphonate therapy initiated for the treatment of HO during the 6th post-operative week. After cessation of etidronate use, phosphate levels gradually returned to normal over 2 weeks.

DISCUSSION: Hyperphosphatemia is a rare complication of etidronate use. It is speculated to result from increased renal tubular phosphate reabsorption and is usually asymptomatic. Although mostly asymptomatic, this complication must be kept in mind while administering etidronate to SCI patients and blood phosphate levels should be monitored in the early weeks of treatment.