These are disorders caused by insufficient levels of vitamin D in the body.
They are really the same condition: rickets is the name used when it occurs in children whereas osteomalacia is the term used for adults.
Where do we get vitamin D from?
There are two sources of vitamin D:
a person’s diet
formation in the skin through exposure to sunlight.
There are few dietary sources of vitamin D.
The best ones are fatty fish – such as salmon, tuna and sardines. Margarine and a few other foodstuffs are supplemented with vitamin D.
Milk contains added vitamin D in the USA but not in the UK. Human milk is a poor source of vitamin D, but infant formula is fortified with vitamin D.
Most people even in the UK get most of their vitamin D from exposure of the skin to sunlight. The average person has enough vitamin D stored in their body to last for two or three years.
Who is at risk of vitamin D deficiency?
People who get little exposure to sunlight are most at risk of vitamin D deficiency in the UK. Immigrants from Asia and Africa, particularly women and children, are at risk, as are elderly people who are housebound or confined to residential and nursing homes. Anyone whose illness or lifestyle makes outdoor activities difficult is at risk. Recent surveys have shown that significant vitamin D deficiency is not uncommon in the general population.
Some people with intestinal problems, such as Crohn’s disease, coeliac disease and cystic fibrosis, may also become short of vitamin D, as do some patients with liver disease.
An infant’s vitamin D status is entirely dependant on that of its mother. If a mother is deficient, the infant may be born with rickets or have fractures in early life.
What are the symptoms of osteomalacia and rickets?
Osteomalacia: bone pains and muscle weakness are the classical symptoms. Fractures can occur. Fractures may take place with little or no recognised trauma. Nowadays increasing numbers of patients without any symptoms are identified after the finding of a low bone density.
Rickets: aches and pains, and sometimes visible enlargement of bones at joints, such as the wrists. Fractures may occur without recognised trauma. Some infants with rickets have convulsions.
How do we test for vitamin D deficiency?
Simple blood tests for levels of calcium, phosphate and alkaline phosphatase are often helpful in pointing to osteomalacia in adults.
More specific blood tests are needed to confirm the diagnosis. These include measurements of the levels of 25- hydroxyvitamin D, the main form of vitamin D in blood, and of parathyroid hormone.
Some patients but not all have a reduced bone density on bone density scanning.
In children X-rays, particularly of the wrists and knees, are useful. But normal appearances do not exclude rickets. The blood calcium level may be low but tests for levels of phosphate or alkaline phosphatase may be difficult to interpret in children. Blood tests for 25-hydroxyvitamin D and parathyroid hormone are also important.
What treatment is available?
Regular daily supplements of vitamin D with or without calcium are usually used for people with simple vitamin D deficiency.
An alternative is a single large oral dose or injection of vitamin D. This is stored in the body and can last up to a year before another injection may be needed. People with vitamin D deficiency due to intestinal problems are best treated with calciferol injections.
Most people with osteomalacia find their pain is reduced about two weeks after the injection. Extra calcium may also be needed while bone is healing.
Are there forms of rickets not caused by lack of vitamin D?
Infants born prematurely sometimes have a bone problem, including spontaneous fractures in the first few months of life.
This condition, bone disease of prematurity, is sometimes referred to as rickets. But there is no evidence that lack of vitamin D is the cause.
Uncommon types of rickets are caused by inborn defects in the way vitamin D is handled in the body.
X-ray changes similar to those of rickets result from phosphate depletion, usually because of inborn renal defects.