15-YEAR-OLD FEMALE WITH SPONTANEOUS XLH*

  • Birth: full-term infant with no abnormalities detected
  • 12 months: signs consistent with pain upon weight bearing; limping; bowed legs at 18 months
  • Family history: unremarkable
  • 30 months: X-rays – bilateral bowing with irregular and widened metaphyses at tibia and femur
  • 34 months: key fasting laboratory findings (reference range)
    • Serum phosphorus: 2.4 mg/dL (4.3-6.8 mg/dL)
    • 25-hydroxyvitamin D: 39 ng/mL (≥20 ng/mL)
    • Alkaline phosphatase: 512 U/L (156-369 U/L)
    • Serum calcium: 9.2 mg/dL (9.2-10.5 mg/dL)
    • Parathyroid hormone: 85 ng/L (10-65 ng/L)

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Growth Chart
15-year-old female history of growth chart
History of growth progression. Patient had short stature. Linear growth accelerated from 8 to 10 years of age, consistent with early growth spurt.
The reference percentiles on the graph are combined from the two clinical growth charts for girls 2-20 years of age provided by the Centers for Disease Control and Prevention.
  • Spontaneous X-linked hypophosphatemia (XLH)
  • Treatment: oral calcitriol and phosphate
  • 1-3 years of age: managed under orthopedic care
    • Optimal control of metabolic bone disease difficult to achieve
    • Patient had short stature (See Growth Chart)
  • 3 years of age: referred to endocrinology
  • 5.9 years of age: musculoskeletal presentation with limb deformity
    in femur, tibia, and fibula; rachitic changes (See X-ray 1)

Although this patient’s laboratory results improved, there was no height velocity increase. At 3 years of age, it was concluded that biochemical optimization was not met; patient was then seen monthly to tailor therapy.

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X-ray 1: Limb Deformity
15-year-old X-ray of limb deformity
5.9 years of age: Limb deformity: femur, tibia, and fibula; rachitic changes; lateral angulation at left knee.
  • 7 years of age: metabolic bone disease under control
    • Surgery of lower left extremity discussed, postponement recommended
    • Reported some classmates teased her for wearing a brace
    • Parents reported good activity level
  • 3 to 9 years of age: growth velocity normal (See Growth Chart)
  • 9.5 years of age: musculoskeletal presentation at prominent genu valgum, severe angulation at left knee with knees touching (See X-ray 2)

As this patient matured, awareness of disability and obvious orthopedic deformities increased. Regardless of provider, asking about her mental health was an important element of care.

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X-ray 2: Severe Left Knee Lateral Angulation
15-year-old X-ray of severe left knee lateral angulation
9.5 years of age: Prominent genu valgum of left lower extremity; severe lateral angulation at left knee, with knees touching; 16 cm between medial malleoli, minimal medial angulation of right lower extremity; wide-based gait.
  • 10 years of age: linear growth accelerated consistent with early growth spurt; patient was at the 5th percentile for height (See Growth Chart)
    • Underwent bilateral epiphyseal arrest surgery (epiphysiodesis) (See X-ray 3)
    • Increasing complaints of muscle weakness and left hip, leg, and back pain
    • Tired very easily and could walk only short distances without resting

Linear growth in children with XLH tends to stop at an earlier age than in unaffected children.2,3

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X-ray 3: Windswept Deformity
15-year-old X-ray of windswept deformity
10 years of age: Epiphyseal arrest surgery; windswept deformity.
  • Limb deformity worsened despite treatment with oral calcitriol
    and phosphate

    • Exhibited signs of secondary varus of right knee as in windswept deformity
  • Between 12.5 and 14.5 years of age: patient underwent successful osteotomies of femurs and left tibia (See X-ray 4)
  • Homeschooled

Once growth potential was reached, XLH management continued, including monitoring of biochemical bone health to promote healing and peak bone mass. As the patient aged, her treatment management transitioned from promoting bone growth to fracture prevention and maximizing musculoskeletal health.

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X-ray 4: Osteotomies
15-year-old X-ray of osteotomies
12.5-14.5 years of age: Osteotomies of femurs and left tibia.
15-year-old case summary timeline
  • Specialist referral was key to early disease management
  • The goal of treatment management aimed to optimize bone health before growth plate closure
  • Regardless of provider, asking about mental health was an important element of care
  • Linear growth in children with XLH tends to stop at an earlier age than in unaffected children2,3
  • Once growth potential was reached, management of XLH was not over; goals shifted from promoting bone growth to fracture prevention and maximizing musculoskeletal health

*The information for this case study was provided courtesy of Dr. Anthony Portale, Director of the Pediatric Dialysis Program, UCSF Benioff Children’s Hospital, San Francisco. This case study represents a real patient and is intended to be illustrative, not a recommendation for treatment or management. This case study does not claim to represent typical results.

 

Indicates normal range, age, and sex matched. Note that normal range values may vary depending on reference dataset. These ranges were provided by the treating physician.

Reference:

1. Centers for Disease Control and Prevention. Clinical growth charts. 2 to 20 years: girls. Centers for Disease Control and Prevention. Published May 30, 2000. Accessed March 14, 2022. https://www.cdc.gov/growthcharts/data/set2clinical/cj41c072.pdf