Background/Purpose: Hypophosphatasia is a rare metabolic disease caused by loss-of-function mutation(s) in the gene encoding the tissue non-specific alkaline phosphatase (ALP). In children, low tissue non-specific ALP activity leads to deficient skeletal mineralization and complications that may include poor growth, proximal muscle weakness, pain, and compromised physical function. The impact of these symptoms on health-related quality of life is not known.

Methods: The Short Form-10 (a short version of the Child Health Questionnaire) was administered as part of the internet-based Hypophosphatasia Impact Patient Survey (HIPS) developed to characterize the burden of disease in patients with hypophosphatasia. Outreach from 2009-2011 by patient advocacy groups provided awareness of the survey to patients or caregivers and invited participation. Summary statistics were calculated for the norm-based Physical Health and Psychosocial Summary scores (healthy population mean=50, standard deviation [SD]=10) and for each individual question.

Results: Forty-four children (50% male, 80% via caregiver respondents) participated in the Hypophosphatasia Impact Patient Survey, of which 39 completed the Short Form-10. Mean (SD) age at the time of the survey was 6.8 (4.8) years; age at onset of hypophosphatasia symptoms was 0.9 (1.0) years. The majority of children reported pain (82%, 38/44), including in the joints (61%, 27/44) and bones (52%, 23/44), and muscle weakness (66%, 29/44). Thirty-six percent (16/44) reported fractures. The mean Physical Health score (23.7, 95% confidence interval [CI]: 17.2-30.3, n=39) was >2 SD below normal. The mean Psychosocial Summary score (45.6, 95% CI: 41.9-49.3, n=39) revealed a small decrease relative to population norms. The majority of children reported limitations in high energy activities such as riding a bike or skating (79%, 31/39); basic activities such as bending, lifting, and stooping (64%, 25/39); and school work or activities with friends (62%, 24/39) due to physical health problems. Eighty-two percent (32/39) reported experiencing pain in the past 4 weeks. Behavioral and emotional problems limited school or social activities in 33% (13/39) of children, and behavior was rated by the respondent as “Good” or higher for 90% (35/39) of the children.

Conclusion: As reported by caregivers/patients and consistent with the reported burden of symptoms, hypophosphatasia has a high physical impact on children which reduces their ability to keep up with peers and participate in normal childhood activities, including both high energy and daily living activities, substantially diminishing health-related quality of life. The lower impact of hypophosphatasia on psychosocial health reported herein may reflect higher resilience to disease in children compared with adults, or the influence of parental report. An understanding of the impact of hypophosphatasia on health-related quality of life is important for evaluating future treatment options. Further studies are needed to characterize health-related quality of life longitudinally in these patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/diminished-health-related-quality-of-life-as-measured-by-the-short-form-10-in-children-with-hypophosphatasia/