It results from deficiency of vitamin D in the diet. Healthy bones cannot be built up without calcium (or lime) salts, and the body cannot use these salts in the absence of vitamin D. Want of sunlight and fresh air in houses or flats where children are reared is also of importance. Once a common condition in industrial areas, it had almost disappeared in Great Britain but has recurred in recent years, largely amongst children of Asian and African origin.

The periosteum – the membrane enveloping the bones – becomes inflamed, and the bone formed beneath it is defective in lime salts and very soft. Changes also occur at the growing part of the bone, the epiphyseal plate.

The symptoms of rickets most usually appear towards the end of the first year, and rarely after the age of five. The children are often ‘snuffly’ and miserable.

Gradually, changes in the shape of the bones become visible, first chiefly noticed at the ends of the long bones. The softened bones also tend to become distorted, the legs bending outwards and forwards so the child becomes bow-legged or knock-kneed. Changes occur in the ribs (‘rickets rosary’)and cranial bones, while teeth appear late and decay or fall out.

The disease usually ends in recovery with more or less of deformity and dwarfing – the bones, although altered in shape, becoming ultimately ossified.

The specific remedy is vitamin D in the form of calciferol (vitamin D2). A full diet is of course essential, with emphasis upon a sufficient supply of milk. Rickets is very rare in breast-fed children but it is a wise precaution to give breast-fed babies supplementary vitamin D. After the child is weaned, the provision of suitable food is vital, supplemented with some source of vitamin D. Regular exposure to sunlight is desirable.

Deficiency of vitamin D in adults results in osteomalacia (see under BONE, DISORDERS OF). (See also APPENDIX 5: VITAMINS.)