FFinalistSouthampton · 2027
Endocrine
AKT · Endocrine/Calcium, bone & parathyroid

Osteomalacia / rickets

Defective bone mineralisation (vitamin D deficiency)

Overview

Defective mineralisation of bone matrix, usually from vitamin D deficiency (low sunlight, malabsorption, CKD, anticonvulsants). In adults = osteomalacia (bone pain, proximal myopathy, pseudofractures); in children with open growth plates = rickets (bowing, swollen joints, growth failure). Biochemistry: low/normal calcium and phosphate with HIGH ALP and low vitamin D; treated with vitamin D (± calcium).

Recognise

  • Adults (osteomalacia): diffuse bone pain/tenderness, PROXIMAL myopathy (waddling gait, difficulty rising), fragility/pseudofractures (Looser zones)
  • Children (rickets): bowing of legs, swollen wrists/costochondral junctions ('rachitic rosary'), delayed fontanelle closure, growth failure
  • Biochemistry: low/low-normal calcium and phosphate, HIGH alkaline phosphatase, low vitamin D, raised PTH (secondary hyperparathyroidism)

Red flags

  • Hypocalcaemic seizures/tetany (severe) → calcium
  • Atypical/refractory rickets → consider hypophosphataemic (X-linked) rickets or renal cause

Differentials & how to tell them apart

OsteoporosisNORMAL calcium/phosphate/ALP; painless until fracture; reduced density not defective mineralisation
Hypophosphataemic (X-linked) ricketslow phosphate with normal vitamin D, renal phosphate wasting — needs phosphate + active vitamin D
Renal osteodystrophy (CKD)CKD with high phosphate, secondary/tertiary hyperparathyroidism
Paget's / metastasisraised ALP but with different calcium/clinical picture

Investigations

Vitamin D (low), calcium/phosphate (low-normal), HIGH ALP, raised PTH; X-ray (Looser zones in osteomalacia; cupped/frayed metaphyses in rickets). Exclude malabsorption/coeliac, CKD.

Management

Vitamin D replacement (± calcium); treat the underlying cause

  1. 1Confirm low vitamin D with high ALP and raised PTH. Replace vitamin D (loading + maintenance) with adequate calcium; treat the cause (sunlight, malabsorption/coeliac).Gate: Use ACTIVE vitamin D (alfacalcidol) in CKD or hereditary forms where 1-α-hydroxylation/handling is impaired; identify hypophosphataemic rickets (renal phosphate wasting) which needs phosphate, not just vitamin D
  2. 2Treat malabsorption/coeliac/renal disease; monitor calcium/ALP normalisation and symptom/radiological recovery.
Vitamin D (colecalciferol) ± calcium — replacement corrects the deficiency; loading then maintenance
Active vitamin D (alfacalcidol) — for CKD or hereditary forms (where activation/handling is impaired)

Key points

Bone pain + proximal myopathy + high ALP + low vitamin D = osteomalacia (rickets in kids: bowing, rosary). Contrast with osteoporosis (normal biochemistry, painless). Treat with vitamin D — active form in CKD.

Monitor & prognosis

Vitamin D, calcium, ALP, PTH; symptoms.

Reversible with replacement.

Source: NICE CKS Vitamin D deficiency; RCPCH (rickets)