See how CRYSVITA may help your patients with XLH

4-year-old male with spontaneous XLH*

Medical history

    Pediatric evaluation

  • 20-month-old male presented with bowed legs
    • Bowing present since birth, worsened once patient started walking
  • Other physical exam findings: waddling gait, cannot run well
  • Suspected diagnosis: congenital bilateral knee bowing
  • At 24-month exam, worsened bowing of legs and waddling gait noted
  • X-ray findings: bilateral bowing of femur and tibia; cupping of distal femur, proximal and distal tibia and fibula
  • Suspected diagnosis: rickets

    Endocrinology and genetics evaluations

  • Physical exam at 24.5 months: severe knee bowing, intercondylar distance 5 cm, short stature, height: 1st percentile (see Growth chart, A)
  • X-rays: metaphyseal flaring at wrists and ankles
  • Laboratory findings (see Table)
  • Suspected diagnosis: hypophosphatemic rickets
  • Upon genetic evaluation at 25 months, pathologic PHEX variant identified, mother negative

Growth Chart

  • Patient growth evolution prior to and after CRYSVITA.
    A: At 24.5 months, the patient was in the 1st percentile for height.
    B: At enrollment, the patient was in the 5th percentile for height.
    C: While on CRYSVITA, the patient was in the 10th percentile for height.
  • The reference percentiles on the graph are combined from the two clinical growth charts for boys 2-20 years of age provided by the Centers for Disease Control and Prevention.

Diagnosis and initial treatment

  • Spontaneous XLH
  • Treatment: oral calcitriol and phosphate

Disease progression

    Evaluation at academic center

  • Physical exam at 29 months: femoral bowing; obvious genu varus – knees 4.5 cm apart, ankles touching; bilateral tibial bowing
  • X-rays: metaphyseal widening at wrists, mild cupping of distal radius and ulna
    • Knees: marked bowing, cupping and fraying of growth plates (see X-rays)
  • Laboratory findings (see Table)
  • Enrolled in CRYSVITA clinical trial at 31 months

    CRYSVITA treatment, 64 weeks

  • Physical exam at 46 months: femoral bowing; bilateral tibial bowing
  • X-rays: resolved cupping and fraying of metaphysis of radius and ulna; improved fraying of femoral metaphysis; decreased widening of femoral growth plate (see X-rays)
  • Laboratory findings: tests improved (see Table)

X-rays: Evolution of Rickets and Lower Limb Deformity

Prior to CRYSVITA
(29 months old)

CRYSVITA 40 weeks
(40 months old)

CRYSVITA 64 weeks
(46 months old)

  • Cupping and fraying of growth plates, marked bowing.

Prior to CRYSVITA
(29 months old)

CRYSVITA 40 weeks
(40 months old)

CRYSVITA 64 weeks
(46 months old)

  • Resolved cupping and fraying of metaphysis of radius and ulna; improved fraying of femoral metaphysis; decreased widening of femoral growth plate.

Laboratory test results

Test (reference rangea unit) Results (age)
Early evaluation
(24.5 months)
Prior to CRYSVITA
(31 months)
CRYSVITA 40 weeks
(40 months)
CRYSVITA 64 weeks
(46 months)
Serum phosphorus (4.3-6.8 mg/dL) 2.9 2.9 3.7 4
TmP/GFR (4.0-5.2 mg/dL) n/a 2.8 3.7 4
25(OH)D (≥20 ng/mL) 26 24 36 26
ALP (156-369 U/L) 636 459 283 299
Serum calcium (9.2-10.5 mg/dL) 9.4 9.5 9.6 9.6
PTH (10-65 pg/mL) 56 20 36 23

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  • 25(OH)D, 25-hydroxy vitamin D (calcifediol); ALP, alkaline phosphatase; PTH, parathyroid hormone; TmP/GFR, ratio of tubular maximum reabsorption of phosphate to glomerular filtration rate.
  • aIndicates normal range, age, and sex matched. Note that normal range values may vary depending on reference dataset. The range in this table was provided by the treating physician.

Summary

  • Patient presented with symptoms at 20 months and underwent several specialty evaluations before XLH diagnosis at 25 months
  • Conventional therapy initiated; XLH symptoms continued to progress
  • Patient enrolled in CRYSVITA clinical trial at 31 months
  • After 64 weeks on CRYSVITA, patient demonstrated improvements in laboratory findings and lower limb deformity
  • *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. Not all patients will respond the same to CRYSVITA treatment. Results may vary. This case study does not claim to represent typical results.
Reference
  1. Centers for Disease Control and Prevention. Clinical growth charts. Centers for Disease Control and Prevention website. https:www.cdc.gov/growthcharts/clinical_charts.htm. Last reviewed June 16, 2017. Accessed July 11, 2019.

Growth Chart

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Laboratory test results

Test (reference rangea unit) Results (age)
Early evaluation
(24.5 months)
Prior to CRYSVITA
(31 months)
CRYSVITA 40 weeks
(40 months)
CRYSVITA 64 weeks
(46 months)
Serum phosphorus (4.3-6.8 mg/dL) 2.9 2.9 3.7 4
TmP/GFR (4.0-5.2 mg/dL) n/a 2.8 3.7 4
25(OH)D (≥20 ng/mL) 26 24 36 26
ALP (156-369 U/L) 636 459 283 299
Serum calcium (9.2-10.5 mg/dL) 9.4 9.5 9.6 9.6
PTH (10-65 pg/mL) 56 20 36 23

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