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Vitamin D-Resistant Osteomalacia

Hypophosphatemic and pseudo-deficiency osteomalacia unresponsive to standard cholecalciferol replacement.

Written by: Saygı Hospital Health Guide Editorial Board
Last updated:

This content has been compiled by the Saygı Hospital Health Guide Editorial Board and is periodically reviewed by a specialist physician.

References (5)

This content is for informational purposes only and does not constitute medical advice. You can book an appointment at our Endokrinoloji department. Book Appointment →

What is Vitamin D-Resistant Osteomalacia?

Vitamin D-resistant osteomalacia encompasses several inherited and acquired conditions in which usual cholecalciferol replacement does not normalize calcium-phosphate metabolism or bone mineralization. The differential includes vitamin D-dependent rickets type I (CYP27B1 mutation, defective 1-alpha-hydroxylation), type II (VDR mutation, end-organ resistance), X-linked hypophosphatemic rickets, autosomal dominant/recessive hypophosphatemic rickets and tumor-induced osteomalacia.

Patients show pseudofractures (Looser zones), bowing deformities of the lower limbs, short stature, dental abscesses without caries, and bone pain despite normal 25-OH vitamin D levels. Persistent hypocalcemia, hypophosphatemia, elevated alkaline phosphatase and inappropriate FGF23 levels are diagnostic clues.

Treatment requires the active form of vitamin D (calcitriol or alfacalcidol), high-dose phosphate, and in FGF23-mediated forms, anti-FGF23 monoclonal antibody (burosumab). Lifelong monitoring is essential to avoid hypercalciuria, nephrocalcinosis and hyperparathyroidism.

Symptoms

Bowing of legs and bone deformities
Pseudofractures and pathologic fractures
Short stature and growth failure
Dental abscesses without dental caries
Bone pain and muscle weakness
Waddling gait
Calcium and phosphate not corrected by ordinary vitamin D
Normal 25-OH vitamin D but persistent osteomalacia

Risk Factors

CYP27B1 mutation (vitamin D-dependent rickets type I)
VDR mutation (vitamin D-dependent rickets type II)
PHEX mutation (X-linked hypophosphatemia)
FGF23, DMP1, ENPP1 mutations
Phosphaturic mesenchymal tumor (TIO)
McCune-Albright syndrome with FGF23 excess
Family history of bone deformities or short stature
Failed response to standard vitamin D therapy

When to See a Doctor?

If you experience any of the following symptoms, seek medical attention promptly:

  • Bone deformities or pseudofractures despite vitamin D therapy
  • Persistent hypophosphatemia or hypocalcemia
  • Recurrent dental abscesses in a child
  • Family history with similar findings
  • Need for genetic testing or FGF23 measurement
  • Burosumab eligibility evaluation

Treatment Methods

01
Calcitriol or alfacalcidol (active vitamin D)
02
High-dose oral phosphate (4-6 divided doses)
03
Burosumab for X-linked hypophosphatemia and TIO
04
Calcium supplementation in vitamin D-dependent type II
05
Cinacalcet for tertiary hyperparathyroidism
06
Surgical correction of severe deformities
07
Surgical resection of phosphaturic tumor in TIO
08
Long-term monitoring of urine calcium and renal ultrasound

Which Department to Visit?

You can visit our Endokrinoloji department for these complaints. Our specialist physicians will create the most suitable treatment plan for you.

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Health Disclaimer: The information on this page is prepared for general informational purposes only. It does not replace medical diagnosis and treatment. Please consult your physician for your complaints. Saygı Hospital does not accept responsibility for actions taken based on the information on this page.