Vitamin D Dependent Rickets type 1A (1 alpha hydroxylase deficiency) (VDDR1A)

What is Vitamin D Dependent Rickets type 1A (1 alpha hydroxylase deficiency) (VDDR1A)

Vitamin D Dependent Rickets type 1A is due to a defect in certain enzymes which are responsible for the synthesis of the active form of vitamin D.

This condition is caused by a mutation in the CYP27B1 gene.


  1. 1 alpha hydroxylase deficiency
  2. Vitamin D Dependent Rickets, Type 1A
  3. 1 alpha , 25-Hydroxyvitamin D3 Deficiency Selective
  4. 25 Hydroxycholecalciferol 1 Hydroxylase Deficiency
  5. Vitamin D Dependency, Type 1 VDD1
  6. Pseudovitamin D Deficiency Rickets, Type IA PDDR1A
  7. PDDR IA

Prevalence at birth


Very frequent in the French Canadian population in the Saguenay region of Quebec

Age of onset


Symptoms of Vitamin D Dependent Rickets type 1A

Mandatory symptoms

Very common symptoms

  • Bone pain 
  • Deformed rib cage 
  • Delayed epiphyseal ossification 
  • Elevated alkaline phosphatase of bone origin 
  • Elevated circulating parathyroid hormone level 
  • Enlargement of the ankles 
  • Enlargement of the costochondral junction 
  • Enlargement of the wrists 
  • Failure to thrive 
  • Femoral bowing 
  • Flat occiput 
  • Generalized aminoaciduria 
  • Genu varum 
  • Hypophosphatemia 
  • Increased susceptibility to fractures 
  • Irregular, rachitic-like metaphyses 
  • Motor delay 
  • Muscle weakness 
  • Osteomalacia 
  • Postnatal growth retardation 
  • Rachitic rosary 
  • Secondary hyperparathyroidism 
  • Sparse bone trabeculae 
  • Subperiosteal bone resorption 
  • Tetany 
  • Thin bony cortex 
  • Tibial bowing 
  • Wide cranial sutures 

Common Symptoms

  • Difficulty walking 
  • Frontal bossing 
  • Generalized hypotonia 
  • Short stature

Rare Symptoms

  • Delayed eruption of teeth 
  • Hypocalcemic seizures 
  • Hypoplasia of dental enamel 
  • Irritability 
  • Protuberant abdomen 

Prognosis of Vitamin D Dependent Rickets type 1A

Prognosis is very good with timely treatment


Daily administration of large doses of vitamin D and physiologic doses of calcitriol


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