Rickets Made Easy

Types

Type	Pathology	25(OH) D	1,25(OH)2 D	PTH	Ca	PO4	ALP	Additional clinical findings	Treatment
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 above	Oral calcium 700 mg/day
Phosphate deficiency (Nutritional)	Hypophosphatemia 🡢 Increased renal production of 1,25(OH)2 D	=	↑↑↑	=	=	↓	↑	No features of secondary hyperparathyroidism	Oral supplementation of phosphate
Vitamin D dependent rickets/VDDR type I (pseudo-vitamin D deficiency)	AR inheritance Defect in renal 1α-hydroxylase	↑/=	↓↓↓	↑	↓	↓	↑		Oral physiologic doses of Calcitriol/1,25(OH)2 D: 1-2 mcg/day
Vitamin D dependent rickets/VDDR type II	AR inheritance Receptor defect for 1,25(OH)2 D	↑/=	↑↑↑	↑	↓	↓	↑	Alopecia	Pharmacological 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)
Hypophosphatasia	AR inheritance Error in tissue-nonspecific isoenzyme of ALP (TNSALP) 🡢 Disrupts bone mineralization	=	=	=	↑	↑	↓↓↓	Early teeth loss	Infusion 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)