Summary

Rickets and Osteomalacia are manifestations of the same pathological process: defective mineralisation of osteoid due to Calcium or Phosphate deficiency. Rickets occurs in children with open growth plates (physes), leading to skeletal deformity (bow legs) and growth retardation. Osteomalacia occurs in adults (fused physes), presenting as diffuse bone pain and pseudofractures. The most common cause globally is Vitamin D Deficiency (Nutritional Rickets) due to lack of sunlight or poor diet. However, genetic forms (X-Linked Hypophosphataemia) and renal causes (Renal Osteodystrophy) must be considered in resistant cases. Treatment involves high dose Vitamin D and Calcium supplementation. [1,2]

Key Facts

• Definition:
  • Rickets: Defective mineralisation of the Growth Plate cartilage + Bone.
  • Osteomalacia: Defective mineralisation of Bone (Osteoid) only.
• Pathology: Accumulation of unmineralised osteoid.
• Key Aetiology: Vitamin D Deficiency (Sunlight).
• Signs (Child): Bow legs (Genu Varum), Rickety Rosary (Costochondral junction swelling), Craniotabes (Soft skull), Short stature.
• Signs (Adult): Bone pain, Proximal Myopathy (Waddling gait).
• Biochemistry: Low Calcium, Low Phosphate, High ALP, High PTH.

Clinical Pearls

"The Waddling Gait": Adults with severe osteomalacia often present with a waddle. This is due to Proximal Myopathy (weak glutes/quads) caused by Vitamin D deficiency/Hypophosphataemia affecting muscle function. It is often misdiagnosed as neurological.

"Looser's Zones": The hallmark radiological sign of osteomalacia. These are Pseudofractures (radiolucent lines perpendicular to the cortex) typically found in the femoral neck, scapula, or pubic rami. They represent stress fractures repairing with unmineralised osteoid.

"It's not just diet": If a child has rickets despite Vitamin D supplements, check the kidneys. Renal Rickets (inability to hydroxylate Vit D) or Hypophosphataemic Rickets (phosphate wasting) needs specific active metabolites (Calcitriol), not just basic Vitamin D.

"The Dark Skin Paradox": Melanin creates a natural sunblock. Patients with darker skin (Fitzpatrick 4-6) living in northern latitudes (UK/Canada) are at massive risk of Vitamin D deficiency and require higher supplementation.

         SUSPECTED RICKETS/OSTEOMALACIA
                    ↓
        BLOODS (Ca, PO4, ALP, Vit D)
                    ↓
        CONFIRM ETIOLOGY (Nutritional vs Renal)
        ┌───────────┴───────────┐
    NUTRITIONAL               RENAL / GENETIC
   (Low Vit D)               (Normal Vit D)
        ↓                       ↓
    REPLACEMENT              SPECIALIST
  (Cholecalciferol)        (Active Metabolites)
  (Calcium)               (Calcitriol/Phosphate)
        ↓
    MONITOR ALP
(Should normalize in 3m)

1. Nutritional Rickets

• Vitamin D Replacement:
  • Stoss Therapy: High dose bolus (e.g., 300,000 IU) once, followed by maintenance.
  • Daily: 2000-6000 IU daily for 3 months.
• Calcium: Ensure adequate dietary intake (milk) or supplements.
• Sunlight: Advice on safe exposure.

2. Renal Osteodystrophy

• The kidney cannot activate Vitamin D.
• Treatment: Alfacalcidol or Calcitriol (Already activated forms). Do not give Cholecalciferol (it won't work).

3. Hypophosphataemic Rickets (XLH)

• Defect: PHEX gene mutation. Kidneys dump phosphate.
• Treatment: Phosphate supplements + Calcitriol.
• New drug: Burosumab (Anti-FGF23 antibody).

4. Surgical (Deformity Correction)

• Indication: Severe deformity persisting after medical treatment.
• Guided Growth (Hemiepiphysiodesis): "8-Plates" placed across the growth plate to steer growth. (e.g., stopping the medial side to correct varus).
• Osteotomy: Cutting the bone to straighten it (for severe/adult cases).

• Pathology: Dominant X-linked mutation.
• Mechanism: Defect in PHEX gene -> Overproduction of FGF-23.
• FGF-23: A hormone that tells the kidney to DUMP phosphate.
• Result: Severe hypophosphataemia despite normal Vitamin D.
• Clinical: Very severe bowing, short stature, dental abscesses.
• Management: Burosumab (revolutionary) neutralises FGF-23.

Key Studies

1. Munns et al. (2016): Global Consensus Recommendations on prevention and management of Nutritional Rickets.
2. Carpenter et al. (2011): Guidelines on XLH management.
3. Chick Dame Harriette: The pioneer who discovered the link between sunlight and rickets in Vienna (1919).

What is Rickets?

Bones need calcium to become hard, like concrete needs cement. Without Vitamin D (which comes from sunshine), your body cannot absorb calcium from food. The bones remain soft and rubbery.

Why are his legs bowed?

Because the bones are soft, they bend under the weight of his body when he walks.

Can we fix the bowing?

Yes. In young children, once we give strong Vitamin D and the bones harden, they often straighten out naturally as they grow ("Remodelling"). If they remain bent after a few years of treatment, we can use small plates (Guided Growth) to help straighten them.

Is milk enough?

No. Milk has calcium (the bricks), but Vitamin D is the builder who puts the bricks in the wall. You need the Vitamin D supplement.