II. Definition

III. Epidemiology

  1. Rare now in developed countries
  2. Still, however, occurs in high risk groups
    1. See Vitamin D Deficiency

IV. Risk Factors

  1. Sunlight avoidance
  2. Dark skin
    1. Melanin blocks UV penetration through skin
  3. Infant with only Breast Feeding
    1. Infant formula is supplemented with Vitamin D
  4. Calcium deficient diet
  5. Family History (hereditary form)
    1. Short Stature
    2. Alopecia
    3. Poor Dentition
    4. Bow legged

V. Pathophysiology

  1. Bone fails to mineralize

VI. Types

  1. Nutritional Rickets (Vitamin D Deficient)
    1. Diet deficient in Vitamin D, Calcium, Phosphorus
    2. Inadequate sunlight exposure or dark skin
    3. Malabsorption (see Secondary Rickets below)
  2. Vitamin D Dependent Rickets
    1. Type I: Pseudovitamin D-deficiency Rickets
      1. Autosomal Recessive enzymatic gene defect
      2. Renal 25(OH)D3-1-a-hydroxylase deficiency
    2. Type II: Hereditary Vitamin D resistant (rare)
      1. Autosomal Recessive defect in Vitamin D receptor
      2. Distinguished by high levels of Calcitriol
  3. Vitamin D Resistant Rickets
    1. Familial Hypophosphatemic Rickets
      1. Most common inherited form
      2. X-linked phosphate regulating gene defect
    2. Hereditary Hypophosphatemic Rickets and Hypocalciuria
  4. Secondary Rickets
    1. Underlying renal disease (Renal Osteodystrophy)
    2. Malabsorption (Celiac Sprue, Cystic Fibrosis, IBD)
    3. Rickets of Prematurity
    4. Malignancy
    5. Medications (due to Hypocalcemia, Hypophosphatemia)
      1. Loop Diuretics
      2. Corticosteroids
      3. Aniconvulsants (Phenytoin)
      4. Aluminum-containing Antacids

VII. Symptoms

  1. General
    1. Irritability
    2. Diaphoresis
  2. Presentation in Infants
    1. Seizure Disorder or Tetany secondary to Hypocalcemia
  3. Presentation in Older Children
    1. Failure to Thrive or Short Stature

VIII. Signs

  1. Muscular weakness and poor tone
  2. Abdominal Distention
  3. Scoliosis
  4. Rachitic Rosary (costochondral beading)
  5. Harrison's Grooves
    1. Flaring of ribs at diaphragm level
    2. Groove forms circumferentially across anterior chest
  6. Contracted Pelvis
  7. Pigeon Breast Deformity (Parrot's Bosses)
    1. Sternum projects forward
  8. Frontal bossing of skull with Craniotabes
  9. Knee angulation (Genu Valgum or genu varus)
    1. Especially genu varus in older children
  10. Wrist flaring
  11. Tooth defects
  12. Delayed closure of anterior Fontanel
  13. Osteopenia

IX. Labs: Nutritional Rickets findings

  1. Serum Calcium (ionized or with albumin): Hypocalcemia
  2. Serum Phosphate: Hypophosphatemia
  3. Serum Alkaline Phosphatase: >500 IU/dl
  4. Parathyroid Hormone increased
  5. Renal Function tests (Serum Creatinine, urea nitrogen)
  6. Serum Calcidiol decreased
  7. Urine Calcium decreased
  8. Urine Phosphorus increased

X. Imaging: AP knee or wrist (rapidly growing long bones)

  1. Findings consistent with Rickets at metaphysis and diaphysis
    1. Cupping (scalloping) of metaphysis
    2. Fraying (tattered rope appearance) at metaphysis
    3. Widened metaphysis (splayed)
    4. Diffuse Osteopenia
  2. Differential Diagnosis (similar XRay findings)
    1. Congenital Syphilis
    2. Osteogenesis imperfecta
    3. Child Abuse

XI. Management

  1. Natural or artificial ultraviolet light exposure
  2. See Vitamin D Replacement
  3. See Calcium Supplementation (1500 mg daily)

XII. Prevention

  1. Ultraviolet light exposure for infants
    1. Diaper only: 30 minutes exposure per week
    2. Fully clothed: 2 hours per week
  2. Vitamin D Supplementation
    1. Dosing: 400 IU (10 mcg) Vitamin D daily
    2. Indication: Breast-fed infants
      1. Mothers not exposed to adequate sunlight
      2. Infants born during cold winters

XIII. Resources

XIV. References

  1. Heird in Behrman (2004) Nelson Pediatrics, p. 186-9
  2. Drezner in Goldman (2004) Cecil Medicine, p. 1555-62

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