Osteomalacia & Rickets

Both are disorders of defective bone mineralisation, usually from vitamin D deficiency — osteomalacia in adults, rickets in children.

Osteomalacia

Incomplete bone mineralisation and loss of bone strength, usually from vitamin D deficiency (also severe CKD and hypophosphataemia).

• Features: bone and muscle pain, muscle weakness, fragility fractures; limited sun exposure.
• Investigations: low vitamin D (<20 nmol/L), low calcium and phosphate, raised PTH and raised alkaline phosphatase, reduced BMD.
• Management (vitamin D deficiency): colecalciferol 4000–7000 IU/day for 4–8 weeks, then reduce to 1000–2000 IU/day; continue 6–12 months. Ensure calcium intake ~1300 mg/day. Recheck ALP, 25-OH vitamin D, calcium, phosphate and PTH every 3 months.

Rickets

Inadequate mineralisation of growing bone in children, causing bowing/distortion, bone pain and fractures. In developed countries most cases are vitamin D deficiency (also nutritional deficiency, severe kidney disease, X-linked hypophosphataemia).

• Investigations: vitamin D, calcium, phosphate, PTH.
• Management: vitamin D supplementation where deficiency is the cause — muscle strength and bone pain improve within weeks (neonate ~1000 IU/day, more in larger children).