We describe the clinical outcome of
asfotase alfa therapy in a 16-year-old boy with severe
childhood hypophosphatasia (
HPP), who began
therapy at age 15 years. The patient was diagnosed with
HPP at age 2 years when he presented with
genu varum and premature loss of primary teeth. He had a history of
multiple fractures requiring 16
orthopedic surgeries with rod and pin placement in his lower extremities. He had chronic skeletal
pain and used
cane to ambulate with great difficulty. His height Z score at age 15 years was - 5. He had severe
scoliosis and
deformity of both legs. Bone radiograph showed hypomineralization and characteristic "tongues" of radiolucency in the distal radius and ulna. His serum
alkaline phosphatase level was stable, with elevated serum
pyridoxal 5'-phosphate and urine
phosphoethanolamine, consistent with
HPP. He was started on
asfotase alfa 2 mg/kg given subcutaneously thrice weekly. He had marked clinical improvement in mobility with no report of
pain after 3 months of treatment. At 6 month, he walked without
cane and participated in outdoor activities with peers. Bone radiograph at 6 months showed striking improvement in previous radiolucent areas. At 9 months, his annualized growth velocity was 9.5 cm/year, while growth velocity of arm span was 12 cm/year. However, at 12 months, he was noted to have worsening
scoliosis from 60 degrees before
therapy to 110 degrees, with a slight decrease in height, necessitating a
spinal fusion surgery. In conclusion, treatment with
asfotase alfa significantly improved physical function,
pain, overall quality of life, and skeletal radiographic findings in this patient. Close monitoring for progression of
scoliosis in adolescents with
HPP treated with
asfotase alfa is recommended.