Cataracts, childhood - Causes of cataracts in children

There are a number of different reasons why a child may be born with cataracts or develop them while they are still young, although it is not possible to determine the exact cause in many cases.

Some of the main causes of childhood cataracts are described below.

Genes and genetic conditions

Cataracts present from birth (congenital cataracts) are sometimes caused by a faulty gene being passed to a child from their parents. This fault means that the lens does not develop properly.

It's estimated that there is a family history of congenital cataracts in around one in every five cases of the condition.

Cataracts can also be associated with conditions caused by chromosome abnormalities, such as Down's syndrome. Chromosomes are the parts of the body’s cells that carry the genes.

Infections in pregnancy

Congenital cataracts can also be caused by infections caught by the mother during pregnancy. The main infections linked to an increased risk of congenital cataracts include:

• rubella (German measles) – a viral infection that can cause a red-pink spotty skin rash
• toxoplasmosis – a parasitic infection caught by consuming food, water or soil contaminated with an infected cat's faeces
• cytomegalovirus (CMV) – a common virus that usually causes few symptoms
• chickenpox – a mild but highly infectious condition caused by the varicella-zoster virus 
• herpes simplex virus – a type of virus that often causes cold sores

Causes of acquired cataracts

Cataracts that develop in children at some point after they are born are known as acquired, infantile or juvenile cataracts.

Causes of this type of cataracts can include:

• galactosaemia – where the sugar galactose (which mainly comes from lactose, the sugar in milk), cannot be broken down by the body 
• diabetes – a lifelong condition that causes a person's blood sugar level to become too high
• eye trauma – as a result of an injury to the eye or eye surgery
• toxocariasis – a rare parasitic infection that can sometimes infect the eyes, spread from animals to humans via their infected faeces

However, most of these problems are either rare or don't normally cause cataracts to develop in children.