Rickets and Vitamin D Deficiency

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(adapted from PowerPoint Presentation by Drs. Lescher and Singleton)
Pathophysiology:

  • Failure of mineralization of growing bone and cartilage
  • A state of extreme vitamin D deficiency
  • Peak incidence between 3 and 18 months of age

Risk Factors:

  • insufficient dietary intake and sun exposure
  • darker skin color and use of sunscreen
  • breastfeeding exclusively without Vitamin D supplementation
  • Northern Latitudes (above 37 deg Latitude)
  • Anticonvulsants, Antifungals, glucocorticoids
  • Limited intake of foods high in Vitamin D (very few exist naturally; however, the Native diet is high in Vitamin D, but the number of children on an exclusive Native diet is decreasing)
  • Obesity

Signs/Symptoms:

  • Irritability, pain, gross motor developmental delay, poor growth
  • Widening of the wrists and ankles, Genu varum or valgum, Prominent costochondral junction (rachitic rosary), Delayed closure of fontanels, Craniotabes, Frontal bossing
  • Delayed tooth eruption, increased risk of caries
  • Increased susceptibility to infections
  • Severe hypocalcemia—tetany, seizures (more often infancy or adolescence with increased growth velocity). usually asymptomatic until serum Ca<7.5mg/dl

Diagnosis:

  • Radiologic studies: Wrist or Knee XRays
    • Osteopenia, cortical thinning of long bones
    • Stress fractures
    • Metaphyseal widening and fraying, splaying, cupping
  • Laboratory studies: Alk Phos is a good screen for rickets; 25OHD level is needed for assessment of Vitamin D status
    • Hypophosphatemia, varying degrees of hypocalcemia
    • Increased alkaline phosphatase
    • Increased PTH
    • Low 25OHD levels

Management:

  • Replace vitamin D and calcium (Proposed treatment plans by AAP):
    • Pharmacological doses of vitamin D: 1000-10,000 IU per day for 8-12 weeks depending on age of the child, then maintain at 400-1000 IU per day
      • 1000-5000 IU/day up to age 1, >5000 IU/day after age 1
    • Stoss therapy: 100,000 – 600,000 IU vitamin D orally, over 1-5 days, then maintain at 400-1000 IU vitmain D per day or 50,000 IU vitmain D2 weekly for 8 weeks (teens and adults only)
    • Calcium: 30-75 mg/kg/day elemental Ca in 3 divided doses (start at higher dose, then wean down to lower end of the range over 2-4 weeks
    • May also need Calcitriol (1,25D) if hypocalcemic
  • Monitoring of therapy (proposed, by AAP)
    • At 1 month: measure Ca, Phos, Alk Phos
    • At 3 months, measure Ca, Phos, Mg, Alk Phos, iPTH, 25OHD, urine Ca/Cr and recheck X-rays
    • At 1 year and annually, measure 25OHD
  • If symptomatic from severe hypocalcemia
    • Slow (<1 ml/min) IV infusion 10% Ca gluconate 1 ml/kg
      • 100 mg/ml Ca Gluconate = 9 mg/ml elemental Ca
      • Cardiac monitoring (bradycardia, shortened QTc due to IV Ca); close attention to infusion site if not central IV (risk of tissue necrosis if peripheral IV infiltration)
    • If Mg low, replace with 0.1-0.2 ml/kg 50% Mg Sulfate

Critical Times for Affected Patients (When to refer to Endocrinology):

  • If no healing after 3 months of Vit D and Ca replacement
    • Concern for malabsorption, liver disease, adherence
  • When considering other causes of rickets (not Vit D deficiency)
    • Rickets <6 months old or between 3 and 10 years old
    • Xrays that show periostal reaction and moth-eaten metaphysis rather than splaying, cupping, etc.
    • Normal levels of AlkP, 25OHD, very low or very high levels of 1,25OHD, high BUN and Cr
  • Severe hypocalcemia

Resources:

Common/Unique Medical Diagnoses