What is galactosemia? Its symptoms and diagnosis?

Galactosemia is a congenital disease that prevents the metabolism of galactose, a lactose sugar. It usually manifests itself in the first weeks of life, and if it is not detected and treated in time, it is lethal.

Galactosemia is a congenital disease. People born with it and is for all of life, and its origin is genetic, i.e., that its origin is an error in the sequence of DNA in a gene on chromosome 9 is an Autosomal recessive disease –transmissible from parents to children if both parents have the defect even though they do not express it–, and affects men and women in the same way. It is a rare disease; its incidence is approximately 1 in 50,000 people.

It is considered a metabolic disease since it consists of an alteration of the intermediate metabolism –responsible for transforming the food we eat into our body’s energy and components–which prevents the patient from correctly metabolizing galactose, a lactose sugar.

When we go down to the molecular level, foods can be divided into three groups: carbohydrates (or sugars), fats, and proteins. Each of these groups is treated or metabolized for one of the following objectives: to convert it directly into energy, to store it in the form of deposits that will later be used to produce that energy, or to transform it to convert it into elements of our body.

This process, which has multiple paths and tracks, could somewhat resemble an assembly or disassembly line and is carried out in successive steps. Each step is executed by a body protein or enzyme (which would be the operator’s equivalent). When there is an error in any of the enzymes (as if the operator was not going to work), the previous product (or metabolite) accumulates, it piles up. Although there are regulatory mechanisms, these accumulations of metabolites are sometimes toxic to the body.

This is the basis of galactosemia, which is that patients cannot tolerate or metabolize galactose. Galactose is a carbohydrate that we ingest with breast milk and with the milk of cows or other animals, which constitutes 50% of lactose. Lactose is a sugar made up of two sugars: glucose (which galactosemia sufferers do tolerate) and galactose. 

When the enzyme does not exist, there is little quantity, or it is defective, accumulating previous metabolites, which are diverted to another pathway, leading to the accumulation of galactitol. The collection of this metabolite in the liver, brain, kidneys, and other organs produces classic galactosemia manifestations. There are different types of galactosemia due to the alteration of other enzymes, but they are rare. In any case, the key is to detect it in time, in the first weeks of life, to control it and avoid greater evils.

Symptoms of galactosemia

Galactosemia is a complex disease to diagnose. It usually manifests itself in the first weeks of life, although there are partial forms in which the patient conserves more of the enzyme, which can be diagnosed in adulthood.

The symptoms of galactosemia in the first weeks of life include poor weight gain, repeated vomiting, hypoglycemia, dehydration, jaundice persistent beyond the early few days, renal failure, and neurological symptoms such as difficulty walking.

Galactosemia can progress over weeks to liver failure. Since the liver is responsible for manufacturing clotting factors, bleeding can occur, and it may be difficult to stop bleeding in the event of injuries.

Generalized infection or sepsis by a bacterium called Escherichia coli is typical in galactosemia. Cataracts are also common, even in the first weeks of life, due to metabolites’ accumulation.

If galactosemia remains undiagnosed, it causes learning problems, language delay, and difficulties in speech development.

In adulthood, galactosemia produces hypogonadism (poor sexual and genital development) and ovarian failure with infertility, short stature, tremors, and other neurological disorders.

Diagnosis of galactosemia

The diagnosis of galactosemia is suspected by the signs and symptoms indicated above – especially if there is lightheadedness, diarrhea or vomiting, and jaundice – through a routine examination by the newborn’s pediatrician. A good clue to the diagnosis is an infant who becomes ill when he eats, improves when he is left on a diet with only intravenous fluids, and worsens again when he eats again.

This problem can also be suspected if there is a known history of galactosemia in the family, which can be verified with a sample of amniotic fluid taken through amniocentesis or a chorionic villus test (the sample is taken from the placenta ).

The urine reducing sugar test, which consists of introducing a special pill into the patient’s urine and seeing if the color changes to a particular shade, indicates disease.

The definitive diagnosis of galactosemia is made by determining galactose-1-phosphate-uridyl transferase in the blood. A test is done only in some specialized laboratories.