What is rickets?
Rickets - the cause of fractures in a young baby whose parents were wrongly accused of his murder - was once almost eradicated.
But factors including poor diet and a lack of exposure to sunlight mean there has been an increase in cases of rickets in UK children in recent years.
It affects the bones, causing them to become weaker and softer than normal. It can lead to serious bone deformities, such as bowed legs or curvature of the spine.
A lack of vitamin D and calcium is the most common cause.
Our bodies absorb vitamin D from the action of sunlight on our skin and from foods such as oily fish, breakfast cereals and eggs.
Vitamin D is essential for a child to form strong and healthy bones because it helps the body absorb calcium from food.
Rare forms of rickets can also be passed on from a parent to a child and, occasionally, rickets develops in children with rare forms of kidney, liver and intestinal conditions.
Babies born prematurely are also at risk of developing rickets because the foetus builds up stores of vitamin D while in the womb.
Rickets is usually treated by increasing intake of vitamin D - either by taking supplements, eating more foods rich in vitamin D and calcium or spending more time outdoors in the sunshine.
The condition is more common in children of Asian, African-Caribbean and Middle Eastern origin because their skin is darker and needs more sunlight to get enough vitamin D.
During the winter months in the UK, no one makes vitamin D from sunlight so maintaining levels in our diets is very important.
The Department of Health recommends that all pregnant and breastfeeding women and children aged under five should take a daily supplement of vitamin D.