Treatment of adult hypophosphatasia with teriparatide.

OBJECTIVE

To describe the effects of 24 months of teriparatide therapy in an adult with hypophosphatasia, which thus far has no established medical treatment.

METHODS

A 75-year-old woman with hypophosphatasia was treated with ergocalciferol and calcium supplements for 2 years. She had sustained multiple spontaneous and low-trauma fractures since she was 10 years old. Baseline biochemical values (and reference ranges) were as follows: serum total alkaline phosphatase ranged from 14 to 17 U/L (30 to 110), bone-specific alkaline phosphatase (BSALP) was 5 U/L (14 to 43), serum phosphorus was elevated at 5.4 mg/dL (2.6 to 4.4), and pyridoxal 5'-phosphate was high at 250 ng/mL (5 to 30). At baseline, she had mild secondary hyperparathyroidism (intact parathyroid hormone, 76 pg/mL; reference range, 10 to 65), which was corrected by the calcium supplementation and vitamin D therapy. Dual-energy x-ray absorptiometry (DXA) scanning in 2003 showed L1-L4 bone mineral density (BMD) of 0.786 g/cm2, T score of -3.3, and Z score of -1.7; DXA also showed femoral neck BMD of 0.740 g/cm2, T score of -2.5, and Z score of -0.5. During walking, the patient sustained a low-trauma fracture in a metatarsal. Teriparatide, synthetic parathyroid hormone(1-34), in a dosage of 20 microg subcutaneously was given daily from April 2004 until June 2006.

RESULTS

After about 1.5 years of teriparatide therapy, BSALP reached the lower end of the reference range at 16 U/L, and after 24 months of continuous teriparatide treatment, both serum total alkaline phosphatase and BSALP normalized at 30 U/L and 18 U/L, respectively. Pyridoxal 5'-phosphate declined from a baseline of 250 to 188 ng/mL after 17 months of treatment. Urinary N-telopeptide increased from a baseline of <6 to 19 after 17 months and to 70 bone collagen equivalents/mmol creatinine after 24 months of anabolic therapy. Repeated DXA scanning showed a substantial improvement in lumbar spine BMD and stability in hip BMD. The patient experienced no clinical fractures or adverse events during teriparatide therapy.

CONCLUSION

In one woman with adult hypophosphatasia, 2 years of teriparatide treatment improved biochemical markers of bone remodeling and increased skeletal mineralization. Teriparatide may prove to be a viable treatment for adult hypophosphatasia; thus, this intervention warrants further evaluation.