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Hypophosphatasia (HPP) in children and adolescents can have a lifelong impact.1-3

Manifestations resulting from hypophosphatasia in children and adolescents can include

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  • Skeletal
  • Muscular/Rheumatologic
  • Growth and development
  • Physical function
  • Dental
  • Neurologic
  • Renal
  • Craniosynostosis4
  • Rickets5,6
  • Bowing of the long bones1,7
  • Irregular mineralization/calcification7
  • Widened metaphyses1,8
  • Valgus deformities6
  • Fractures1,9
  • Bone pain1
  • Muscle and joint pain1,10
  • Muscle weakness1,11
  • Delayed or missed motor milestones1,11
  • Short stature1,9
  • Low body weight9
  • Unusual or waddling gait1,11
  • Impaired mobility (including use of assistive devices)1,9
  • Difficulty with activities of daily living9
  • Premature loss of teeth1,12
  • Neurologic complications of craniosynostosis
    • Increased intracranial pressure1,4
    • Seizures13
    • Optic nerve damage4
    • Papilledema1,4
  • Hypercalcemia9
  • Nephrocalcinosis14

Skeletal manifestations of hypophosphatasia can result in a high burden of disease in children and adolescents.1

Defective bone mineralization in hypophosphatasia can lead to fractures and skeletal abnormalities.1,6

7.5 months of age15,a
8.5 years of age6,a
9 years of age16,a
Femoral bowing
Tibial valgus deformity
Fracture of the right femoral neck

Progressive skeletal demineralization can occur over time.17

7 weeks of age15
Same patient at 33 months of age15
Long bones
Long bones barely visible
Hypophosphatasia-related skeletal abnormalities can lead to pain, short stature, delayed walking, and waddling gait.1,11

Children with hypophosphatasia are at high risk of serious systemic manifestations.1,10,18

Hypophosphatasia causes pain and muscle weakness in children and adolescents.1,10,11

A majority of children and adolescents with hypophosphatasia reported experiencing pain and muscle weakness.9

Mobility in children with hypophosphatasia is severely impaired compared with healthy peers.9,20

Children with hypophosphatasia had impaired mobility vs healthy children, as measured by the 6-minute walk test (6MWT).9,20

The 6MWT is a clinically relevant measure of disability for patients with hypophosphatasia.9

The 6MWT assesses ambulatory function, which encompasses lower extremity strength, endurance, and cardiorespiratory status21
Mobility impairments may affect the ability of children and adolescents to participate in normal childhood activities.9

Hypophosphatasia causes functional impairment in children and adolescents.6,9

Children and adolescents with hypophosphatasia reported difficulty with a variety of normal childhood activities.9,h

Hypophosphatasia has devastating consequences on growth, development, functionality, and daily life.1,6,9,11,22

Low alkaline phosphatase (ALP) activity in children and adolescents with hypophosphatasia can lead to ongoing functional impairment that can dramatically impact quality of life.1,6,9,11,22

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Learn about disease progression in an adolescent with hypophosphatasia.

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How might hypophosphatasia impact adults in your practice?

aRadiographs are from different patients with hypophosphatasia.

bData from a noninterventional, retrospective chart review study designed to understand the natural history of 48 patients ≤5 years of age with severe perinatal- and infantile-onset HPP. Patients included in the study were those diagnosed with HPP based on at least one of the following: serum biomarker levels (below-normal ALP and above-normal PLP or PEA), below-normal ALP and radiographic abnormalities, or genetic analysis of the ALPL gene. Additionally, onset of HPP must have occurred prior to 6 months of age based on signs that included at least one of the following: respiratory compromise, rachitic chest deformity, and/or vitamin B6–responsive seizures.19

cData from a retrospective, multinational, noninterventional natural history study of childhood HPP in patients 5 to 15 years of age (N=32).25

dHIPS/HOST combined data from an Internet questionnaire and telephone survey that queried demographics, hypophosphatasia-related illness history, disease progression, and health-related quality of life. Fifty-nine children participated.9

eHIPS was an Internet questionnaire that queried demographics, hypophosphatasia-related illness history, disease progression, and health-related quality of life. Forty-four children and adolescents participated.9

fData from a subset of 9-year-old boys (n=60; mean age, 9.5 years) from a larger study (N=442) intended to generate normative data for the 6MWT.9

gBaseline 6MWT data from a clinical trial in children 5 to 12 years of age with HPP (N=13; mean age, 8.8 years).20

hData from HOST, a telephone survey that queried demographics, HPP-related illness history, disease progression, and health-related quality of life. Fifteen children participated.9

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References:
  1. Rockman-Greenberg C. Hypophosphatasia. Pediatr Endocrinol Rev. 2013;10(suppl 2):380-388.
  2. Bachrach LK. Acquisition of optimal bone mass in childhood and adolescence. Trends Endocrinol Metab. 2001;12(1):22-28.
  3. Davies JH, Evans BAJ, Gregory JW. Bone mass acquisition in healthy children. Arch Dis Child. 2005;90(4):373-378.
  4. Collmann H, Mornet E, Gattenlöhner S, Beck C, Girschick H. Neurosurgical aspects of childhood hypophosphatasia. Childs Nerv Syst. 2009;25(2):217-223.
  5. Whyte MP, Greenberg CR, Salman N, et al. N Engl J Med. 2012;366(10):904-913.
  6. Beck C, Morbach H, Wirth C, Beer M, Girschick HJ. Whole-body MRI in the childhood form of hypophosphatasia. Rheumatol Int. 2011;31(10):1315-1320.
  7. Mornet E, Nunes ME. Hypophosphatasia. In: Pagon RA, Adam MP, Ardinger HH, et al, eds. GeneReviews. Seattle, WA: University of Washington, Seattle; 1993. http://www.ncbi.nlm.nih.gov/books/NBK1150/. Published November 20, 2007. Updated February 4, 2016. Accessed October 26, 2017.
  8. Millán JL, Whyte MP. Alkaline phosphatase and hypophosphatasia. Calcif Tissue Int. 2016;98(4):398-416.
  9. Data on file, Alexion Pharmaceuticals.
  10. Whyte MP, Madson KL, Munns CF, et al. A retrospective, multi-national, non-interventional, natural history study of the childhood form of hypophosphatasia [abstract LB-OR01]. Endocrine Society's 97th Annual Meeting and Expo website. https://endo.confex.com/endo/2015endo/webprogram/Paper22822.html. Accessed October 26, 2017.
  11. Seshia SS, Derbyshire G, Haworth JC, Hoogstraten J. Myopathy with hypophosphatasia. Arch Dis Child. 1990;65(1):130-131.
  12. Reibel A, Maniére M-C, Clauss F, et al. Orodental phenotype and genotype findings in all subtypes of hypophosphatasia. Orphanet J Rare Dis. 2009;4:6.
  13. Craniosynostosis. MedlinePlus website. https://www.nlm.nih.gov/medlineplus/ency/article/001590.htm. Updated October 3, 2017. Accessed October 26, 2017.
  14. Mohn A, De Leonibus C, de Giorgis T, Mornet E, Chiarelli F. Hypophosphatasia in a child with widened anterior fontanelle: lessons learned from late diagnosis and incorrect treatment. Acta Paediatr. 2011;100(7):e43-e46.
  15. Whyte MP, Greenberg CR, Salman N, et al [supplementary appendix]. N Engl J Med. 2012;366(10):S1-S47.
  16. Moulin P, Vaysse F, Bieth E, et al. Hypophosphatasia may lead to bone fragility: don't miss it. Eur J Pediatr. 2009;168(7):783-788.
  17. Whyte MP. Hypophosphatasia. In: Thakker RV, Whyte MP, Eisman JA, Igarashi T, eds. Genetics of Bone Biology and Skeletal Disease. London, UK: Academic Press; 2013:337-360.
  18. Eade AWT, Swannell AJ, Williamson N. Pyrophosphate arthropathy in hypophosphatasia. Ann Rheum Dis. 1981;40(2):164-170.
  19. Whyte MP, Leung E, Wilcox W, et al; for Study 011-10 Investigators. Hypophosphatasia: a retrospective natural history study of the severe perinatal and infantile forms. Poster presented at: 2014 Pediatric Academic Societies and Asian Society for Pediatric Research Joint Meeting; May 3-6, 2014; Vancouver, BC.
  20. Goemans N, Klingels K, van den Hauwe M, et al. Six-minute walk test: reference values and prediction equation in healthy boys aged 5 to 12 years. PLoS One. 2013;8(12):e84120.
  21. McDonald CM, Henricson EK, Abresch RT, et al; for PTC124-GD-007-DMD Study Group. The 6-minute walk test and other clinical endpoints in Duchenne muscular dystrophy: reliability, concurrent validity, and minimal clinically important differences from a multicenter study. Muscle Nerve. 2013;48(3):357-368.
  22. Taketani T, Onigata K, Kobayashi H, Mushimoto Y, Fukuda S, Yamaguchi S. Clinical and genetic aspects of hypophosphatasia in Japanese patients. Arch Dis Child. 2014;99(3):211-215.
  23. Balasubramaniam S, Bowling F, Carpenter K, et al. Perinatal hypophosphatasia presenting as neonatal epileptic encephalopathy with abnormal neurotransmitter metabolism secondary to reduced co-factor pyridoxal-5'-phosphate availability. J Inherit Metab Dis. 2010;33(3):25-33.
  24. Weber TJ, Sawyer EK, Moseley S, Odrljin T, Kishnani PS. Burden of disease in adult patients with hypophosphatasia: results from patient-reported outcome surveys. Poster presented at: Endocrine Society Annual Meeting; March 5-8, 2015; San Diego, CA.
  25. Phillips D, Griffin D, Przybylski T, et al. Gait assessment in children with childhood hypophosphatasia: impairments in muscle strength and physical function. Poster presented at: Endocrine Society Annual Meeting; March 5-8, 2015, San Diego, CA.
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