008–Case Study: 3 Year Old Female with Hypophosphatasia, Treated with Asfotase Alfa Replacement

Abstract

Patient Demographics: J.R. is a 3 year 6 month female of Chinese descent who was adopted at the age of 1 year 8 months. The child’s birth and family history are unknown. Clinical Presentation: Patient presented with short stature (height: 0.03%ile), underweight (weight: 2.9%ile), clubbed feet, and bowing of her legs and arms. Patient had premature tooth loss (2 teeth at 20 months of age and 4 additional teeth by 3 years 6 months.) Sequential growth charts revealed no catch-up growth since age 2yr. Relevant Past History: J.R. showed a history of delayed walking at age 2 yr 6 mo. Mother reports that child complained of consistent lower back and leg pain, requiring orthotics, twister cable braces, and intermittent use of a walker. J.R. also required speech therapy. There is no history of skeletal fractures since adoption. Evaluation: Skeletal survey at 1 yr 9 mo of age showed evidence of 6 fractures in utero. The survey also showed minimally decreased bone mineralization and mild bowing of the bilateral diaphysis. Also seen were bony spurs projecting off lateral aspects of bilateral fibulas with focal overlying skin pitting/dimpling defect. No additional fractures, metaphyseal, epiphyseal, or diaphyseal dysplasia, nor metaphyseal fraying were seen. Labs: Low alkaline phosphatase: 33 U/L (129-291), significantly elevated vitamin B6: 488mcg/L (5-50) and urine phophoethanolamine: 2960 nanomoles/mg of creatinine (180-533) that confirmed the diagnosis of hypophosphatasia. At age 2yr 6mo, J.R. had a normal renal ultrasound that ruled out nephrocalcinosis. At age 3yr 6mo, a modified 5min walk test showed that the child was able to complete 5 laps and an additional few paces. Interventions: J.R was treated with asfotase alfa replacement therapy 2mg/kg SQ 3x/wk. On follow up, she showed improvement in her growth velocity, 5min walk test, muscle strength, and symptom survey. Discussion/Recommendations: Asfotase alfa was FDA approved for treatment of hypophosphatasia in 2015. Endocrine nursing focus should be on continued observation for safety and efficacy of the drug as well as psychological support for the family with a child with special needs requiring long-term injections.