Galactosaemia

What is galactosaemia?

Galactosaemia is condition in which the body cannot process or ‘metabolise’ the sugar galactose. The main dietary source of galactose is lactose, the natural sugar in milk and other dairy products. After milk is ingested an enzyme breaks the lactose down into glucose and galactose. Different enzymes then process the galactose into more glucose to be used by our bodies as energy. In people with galactosaemia, galactose is not metabolised and stays in the blood (hence the name galactos-: galactose; -aemia: in the blood). The levels build up and cause complications such as an enlarged liver, cataracts, brain damage and kidney failure. Untreated, galactosaemia can be life threatening.

What are the incidence and prevalence rates of galactosaemia?

The condition is rare, affecting only 1 in 70,000 people in the UK and 1 in 47,000 Caucasians in America. In Ireland, the condition is slightly more common, affecting 1 in 30,000 people overall, although it may affect as many as 1 in 480 people within traveller communities. People of African or Asian descent are less prone to the disorder than Caucasians. Males are affected as frequently as females and the condition manifests during the very first weeks of life.

What causes galactosaemia?

Galactosaemia is a recessive genetic disorder. It results from an inherited mutation in the gene that makes an enzyme required for galactose metabolism. Mutations limit the ability of genes to generate the products they code for. In most people with galactosaemia, the deficiency is in the GALT enzyme (galactose-1-phosphate uridyltransferase). Less commonly, the enzymes galactokinase or UDP galactose epimerase may be involved.

Genes are arranged in structures called chromosomes that contain two strings or ‘alleles’. Offspring inherit one allele from their father and one from their mother. If a child receives two alleles with the galactosaemia mutation (i.e. one from each parent) they will develop the disorder. Parents will not be aware that they carry a galactosaemia mutation until giving birth to an affected infant. The disease does not manifest itself if the other allele in the chromosome is unmutated. In genetic terms, such parents are known as ‘carriers’ as they harbour and can pass on the genetic error but do not have the disease itself.

For each and every pregnancy, there is a 1 in 4 chance of two carriers having a child with galactosaemia.

What are the symptoms and signs of galactosaemia?

Normally, no abnormalities are obvious at birth. However, symptoms and signs of galactosaemia appear in infants once they are introduced to milk – either breast milk or formula – due to the rapid accumulation of galactose.

The features vary in severity. Early indicators in infants are feeding difficulties, vomiting, failure to gain weight, tiredness, irritability and convulsions.

Examination and tests may reveal the infant to have amino acids in the urine, collections of fluid in the abdomen, clouding of the lens of the eyes (cataracts) or a full fontanelle (the soft area on the baby’s skull). Babies may also develop jaundice, have enlarged livers and show signs of liver damage. Sufferers are prone to E. coli sepsis – a serious inflammation of the whole body due to a bacterial infection.

Additionally, children with galactosaemia show a characteristic delayed development in speech, language and learning. Specifically, there can be problems with organised speech (oromotor dyspraxia) and possibly with movement (motor dyspraxia) making children slow in finishing tasks. Difficulties with maths and reading are also common. The reason for these developmental complications is not known. They can affect many aspects of a child’s life including social and family life, school, work and daily activities.

Females are affected by a number of gynaecological complications of galactosaemia. The majority of adolescent women with galactosaemia do not go into puberty at the right time. Or their periods may stop unexpectedly. This is due to a condition called hypergonadotrophic hypogonadism, which is linked to poor functioning of the ovaries. Women with galactosaemia may also experience premature ovarian failure, which causes infertility. Although some women with galactosaemia are successful in becoming mothers, reduced fertility is a problem for the majority.

Finally, adults with galactosaemia are usually short in height and may suffer coordination problems (ataxia) and tremor.

How is galactosaemia diagnosed?

Galactosaemia is detected in the first few weeks of life since symptoms begin once the infant starts to ingest milk. The greatest indicators of the condition are failure to thrive and E. coli sepsis.

Diagnosis is confirmed by measuring the activity of the galactose-metabolising enzymes in the blood. Tests can also be carried to out to detect galactose or related compounds in the urine.

In the USA and in certain European countries, newborn infants are screened for galactosaemia using a heel-prick test. In the UK, screening is only carried out in Scotland.

How is galactosaemia treated?

Galactosaemia is a lifelong condition, for which there is no cure. However, it can be managed successfully by excluding galactose from the diet. This must be started immediately after diagnosis and only under the advice of a nutritionist. The diet must be followed throughout life.

Galactose-restriction primarily involves avoiding milk and other dairy products including cream, yoghurt, cheese, butter and milk powder due to their lactose content. Certain fruits and vegetables (such as figs and certain peas and beans) contain galactose so total elimination is difficult. A galactose-restricted diet rapidly improves liver problems and infants begin to gain weight. Cataracts also improve over time, and usually resolve completely.

Many prepared foods contain milk or milk products. Some of these may not be so obvious – for example, whey, casein, calcium caseinate and lactalbumin all indicate milk or lactose content, and some food flavourings and colouring such as caramel may contain milk. Food labelling has improved over recent years in the UK in an effort to clarify which products contain milk. Dieticians can provide invaluable guidance on understanding food labelling and lists of milk-free products are available from most supermarkets. Nutritionally complete infant formulas are available for the sole source of nutrition for babies with galactosaemia or as a supplementary feed for older children. Dairy-free and milk-replacement foods and ingredients are available for older children and adults.

Certain complications continue, however, despite dietary galactose reduction. Specialised intervention may be required for speech, language and learning problems. Premature ovarian failure, plus a dairy-free diet, increases the risk of osteoporosis in later life. Calcium supplements, hormone-replacement therapy and regular weight-bearing exercise can help to maximise bone mineral density. Osteoporosis can affect both sexes but is a particular concern for females. Oestrogen therapy may be indicated to trigger puberty in those with hypergonadotrophic hypogonadism. Long-term oestrogen-replacement therapy can help stabilise menstrual cycles. For women requiring fertility treatment, approaches using donated eggs may be an option.

The complications of galactosaemia are not life threatening. Children and adults living with galactosaemia and following a galactose-restricted diet can look forward to an otherwise healthy and active life.