Rickets Made Easy

Rickets vitamin D metabolism
Dr.Vijaya chandar, CC BY-SA 4.0, via Wikimedia Commons

Types

TypePathology25(OH) D1,25(OH)2 DPTHCaPO4ALPAdditional clinical findingsTreatment
Vitamin D deficiency (Nutritional)Hypovitaminosis D 👒 Hypocalcemia 👒 Secondary hyperparathyroidism 👒 Rise of serum calcium towards normal level↓↓↑↓/=↓↑Rachitic rosary
Bowing of knees
Muscle hypotonia
Waddling gait
Dental disease
Looser zones/Milkman’s fracture (pseudofracture on compression side)
Stoss regimen: Vitamin D 3-6 lac IU PO/IM as 2-4 doses in 1 day OR
Oral Vitamin D 2000-5000 IU/day over 4-6 wks
Calcium deficiency (Nutritional)Hypocalcemia 👒 Secondary hyperparathyroidism 👒 Enhanced renal conversion of 25(OH)D to 1,25(OH)2 D and Rise of serum calcium towards normal level=↑/=↑↓/=↓↑Same as aboveOral calcium 700 mg/day
Phosphate deficiency (Nutritional)Hypophosphatemia 👒 Increased renal production of 1,25(OH)2 D=↑↑↑==↓↑No features of secondary hyperparathyroidismOral supplementation of phosphate
Vitamin D dependent rickets/VDDR type I (pseudo-vitamin D deficiency)AR inheritance
Defect in renal 1Ξ±-hydroxylase
↑/=↓↓↓↑↓↓↑Oral physiologic doses of Calcitriol/1,25(OH)2 D: 1-2 mcg/day
Vitamin D dependent rickets/VDDR type IIAR inheritance
Receptor defect for 1,25(OH)2 D
↑/=↑↑↑↑↓↓↑AlopeciaPharmacological doses of Calcitriol or Alphacalcidiol (3-6 mcg/day) for 3-6 months + Oral elemental calcium 3 gm/day
Hypophosphatemic rickets (Vitamin D resistant rickets)X-linked dominant inheritance
Defefct in tubular (PCT) reabsorption of phosphate leading to phosphate “spilling” in urine (phosphate diabetes)
====↓↓↓↑Classic triad:
1. Hypophosphatemia
2. Lower limb deformities
3. Stunted growth rate
Oral elemental phosphate 1-3 gm/day + High dose vitamin D 20,000-70000 IU/day (to counteract hypocalcemic effect of phosphate administration)
HypophosphatasiaAR inheritance
Error in tissue-nonspecific isoenzyme of ALP (TNSALP) 👒 Disrupts bone mineralization
===↑↑↓↓↓Early teeth lossInfusion of plasma rich in ALP activity

Bone marrow transplantation

Clinical features

Mnemonic: RICKETS

  1. Rachitic rosary
  2. Increased lordosis
  3. Craniotabes (<6 months)
  4. Knock knees (>1 year)
  5. Epiphysis enlargement (>6 months)
  6. Teeth eruption delay, Tone decreased, Tetany (<6 months)
  7. Skull bossing, Sternal prominence/pectus carinatum(>6 months), Seizures (<6 months)

Rickets evaluation

Mnemonic: ABCDEF

ALP: If decreased – consider Hypophosphatasia (elevated urinary phosphoethanolamine is diagnostic)

Bicarbonate: Low in Renal tubular acidosis (RTA)

Calcium: Increased/normal in hypophosphatemic rickets (Vitamin D resistant rickets/Albright syndrome) and hypophosphatasia (AR)

D Vitamin level: Increased in Vitamin D dependent rickets (VDDR) or calcium/phosphate deficiency and Normal in hypophosphatemic rickets and hypophosphatasia

  • In VDDR type I, only 1 metabolite is elevated (Calcidiol)
  • In VDDR type II, both the 2 metabolites are elevated (Calcidiol and Calcitriol)

Elevated PTH: Except in hypophosphatemic rickets and hypophosphatasia

FGF23: High in hereditary (XLD) and acquired forms of hypophosphatemic rickets

Fosforous (Phosphorous): High in hypophosphatasia and renal failure

Radiological features

Mnemonic: RICKETS

  1. Rarefaction (osteopenia)
  2. Indistinct cortex
  3. Coarse trabeculation, Coxa vara, Codfish vertebra
  4. Knee, wrists and ankles affected predominantly
  5. Epiphyseal plates widened (earliest and specific), irregular and delayed appearance of ossification centers
  6. Tremendous metaphysis (cupping, fraying, splaying), Triradiate pelvis (protrusion of hip and spine into soft pelvis)
  7. Spur (metaphyseal)


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