Teriparatide treatment in adult hypophosphatasia in a patient exposed to bisphosphonate: a case report.

We describe the case of a woman with hypophosphatasia previously exposed to bisphosphonate and subsequently treated with teriparatide (recombinant human PTH 1-34).A Caucasian woman sustained bilateral femur stress fractures when she was fifty years old, which widened despite use of calcium, vitamin D and risedronate for 2.5 years and required intramedullary rods for stabilization. Hypophosphatasia was diagnosed in the interim due to low serum alkaline phosphatase (ALP) (ALP 20 IU/L; normal (N), 40-150 IU/L) and high pyridoxal 5' phosphate (3400 nmol/L; N 18-175 nmol/L). She was referred for further management. On presentation, she had significant fracture site pain and generalized bone pain (weight bearing and non-weight bearing) - making her walker dependent at home and wheel chair dependent outside home.She could not sleep at night due to discomfort when she moved. Daily teriparatide injections, 20 mcg subcutaneously were prescribed.At 8-weeks follow-up, fracture site pain, weight-bearing and non weight-bearing pain improved significantly allowing ambulation for prolonged periods without assistance. She slept at night without discomfort. Improvement persisted during her entire treatment period. Radiographs taken at 4 and 16 months of treatment demonstrated healing of femur fractures.Biochemically, mean urine cross-link-N-telopeptide increased 11% as compared to her base-line, while bone specific alkaline phosphatase did not increase as expected.In conclusion, we observed an uncoupling of bone formation and resorption markers during her treatment period in the face of notable clinical and radiological improvement. Off-label use of teriparatide may help patients with hypophosphatasia.