Osteomalacia and Rickets (Vitamin D Deficiency)


Osteomalacia (adults) and rickets (children) are caused by an inadequate supply of vitamin D leading to inadequate mineralisation of bone matrix. Vitamin D deficiency causes a low calcium and phosphate, which lead to secondary hyperparathyroidism.
Osteomalacia results from a loss of skeletal mass caused by inadequate mineralisation of the normal osteoid tissue after the closure of the growth plates.1

Rickets results from the same underlying process, occurring in children and adolescents before the growth plates have closed.
Normal bone mineralisation depends on adequate calcium and phosphate and this is maintained by vitamin D. Vitamin D is supplied either in the diet or produced from a precursor in the skin following exposure to ultraviolet light. 90% of our daily vitamin D requirement is usually obtained by the action of sunlight on the skin and 10% is obtained from the diet.

Good food sources of vitamin D include oily fish, liver, egg yolks, fortified margarine and fortified breakfast cereals.
Production of metabolically active vitamin D requires hydroxylation, which occurs first in the liver and then in the kidneys to produce 1,25-dihydroxyvitamin D3.
A 25 hydroxy-vitamin D concentration below around 25 nmol/L (10μg/L) is probably consistent with vitamin D deficiency, which may be associated with osteomalacia. Concentrations of 30-50 nmol/L (12-20μg/L) are generally considered a sign of vitamin D insufficiency, in which there may be biochemical disturbances with or without non-specific musculoskeletal symptoms.2
Epidemiology
It has been estimated that 1 billion people worldwide have vitamin D deficiency.3
One study found the prevalence of rickets in non-Caucasian children to be 1.6%.4
In the UK, the prevalence of vitamin D insufficiency in all adults is about 14.5% and possibly more than 30% in those over 65 years old.2
Risk factors

Dark skin, especially South Asian, African Caribbean and Middle Eastern; prevalence of vitamin D insufficiency is as high as 94% in otherwise healthy South Asian adults25

Children and those aged over 65 years

Pregnancy

Routine covering of face and body, e.g. wearing a veil

Infant who has prolonged breastfeeding without vitamin D supplementation, especially if the mother is vitamin D deficient (increased risk of severe vitamin D deficiency presenting with neonatal fitting)

Housebound or institutionalised

Poverty

Vegetarianism

Alcoholism

Living in countries at high latitude

Family history of vitamin D deficiency

Chronic disease, e.g. malabsorption, renal or liver disease

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