Rickets and Vitamin D Deficiency

(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:

• Vitamin D Supplementation and Screening for the Prevention of Rickets and Osteomalacia in Alaska Recommendations from the Alaska Vitamin D Workgroup [1]
• Singleton, R. et al. Rickets and Vitamin D Deficiency in Alaska Native Children. J Pediatrc Endocrinol Metab. 2015 Jun: 28(0): 815-823. doi: 10.1515/jpem-2014-0446.
• Rickets and Vitamin D Deficiency in Children Powerpoint Presentation by Drs. Lescher and Singleton

Common/Unique Medical Diagnoses