# Galactosaemia

> Galactosaemia for NEET-PG Paediatrics, covering GALT deficiency, E coli sepsis in neonates, cataracts, newborn screening and the lactose-free diet.

- Canonical URL: https://prepelephant.com/topics/neet-pg/paediatrics/galactosaemia
- Exam / course: NEET-PG · Subject: Paediatrics
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-15
- Last updated: 2026-10-15
- Reference basis: Nelson Textbook of Pediatrics; Ghai Essential Pediatrics
- How to cite: "Galactosaemia", PrepElephant, https://prepelephant.com/topics/neet-pg/paediatrics/galactosaemia

## Direct answer

Galactosaemia is an autosomal recessive disorder of galactose metabolism, most often caused by deficiency of galactose-1-phosphate uridyltransferase, or GALT. Affected neonates develop vomiting, jaundice, hepatomegaly and sepsis, often from Escherichia coli, once milk containing lactose is given. Early withdrawal of galactose from the diet prevents most acute features, and it reduces the risk of cataract.

## What you must remember

- **Basic defect:** GALT deficiency blocks conversion of galactose-1-phosphate, which accumulates and damages the liver, brain and lens.
- **Inheritance:** autosomal recessive, so two carrier parents have a 25 per cent risk in each pregnancy.
- **Neonatal presentation:** vomiting, diarrhoea, jaundice, hepatomegaly and failure to thrive appear after milk feeds begin.
- **Sepsis:** Escherichia coli sepsis in a neonate on milk feeds should prompt a search for galactosaemia.
- **Cataract:** galactitol accumulates in the lens and causes cataract, which can develop early in life.
- **Long-term problems:** ovarian failure in girls, and speech dyspraxia or learning difficulties, can persist despite diet.
- **Diagnosis:** newborn screening measures galactose-1-phosphate or GALT activity, and enzyme assay or genetic testing confirms it.
- **Management:** lactose is removed with soy or elemental formula, and breast feeding is stopped.

## Comparing the three galactose enzyme defects

Galactose enters the body through lactose, and the three enzyme defects of galactose metabolism produce different clinical pictures. The table below compares the classic form with galactokinase and epimerase deficiency.

| Defect | Enzyme | Key feature | Diet response |
| --- | --- | --- | --- |
| Classic galactosaemia | GALT | Sepsis, hepatomegaly, cataract, ovarian failure | Lactose-free diet is essential |
| Galactokinase deficiency | GALK | Cataract, usually without systemic illness | Lactose-free diet prevents cataract |
| Epimerase deficiency | GALE | Variable, from benign to severe forms | Diet is individualised |

The classic form matters most for emergency management, because the infant can deteriorate within days of starting milk feeds. Galactokinase deficiency is a milder disorder that is often detected when a cataract is noticed.

Epimerase deficiency is heterogeneous, so the clinical course and newborn screening results guide the decision about diet. Across all three defects, the diagnosis rests on enzyme measurement or genetic testing, not on the clinical picture alone. Families also need to check growth on the substitute formula, and they must read labels, because lactose is used as an excipient in some medicines and processed foods.

## Galactosaemia questions that mislead

Galactosaemia appears in many questions because a single neonatal clue can point to several diagnoses.

- **Trap:** attributing a neonate's vomiting, jaundice and liver enlargement to physiological jaundice or infection alone. — **Correct:** these features with milk feeds should trigger testing for galactosaemia alongside a sepsis work-up.
- **Trap:** assuming the lactose-free diet is enough for life. — **Correct:** ovarian failure and speech or learning problems can persist despite diet, so lifelong follow-up is needed.
- **Trap:** continuing breast feeding after the diagnosis is made. — **Correct:** breast milk contains lactose, so breast feeding is stopped and a galactose-free formula is used.

## Frequently asked questions

### What is the enzyme defect in classic galactosaemia?

Classic galactosaemia is caused by deficiency of galactose-1-phosphate uridyltransferase, abbreviated GALT. Galactose-1-phosphate accumulates and damages the liver, brain and lens. Diagnosis is confirmed by measuring GALT enzyme activity or by genetic testing for GALT variants.

### Why does Escherichia coli sepsis occur in galactosaemia?

Escherichia coli sepsis is a recognised complication of classic galactosaemia in the neonate, often following milk feeds. The mechanism is thought to involve galactose-1-phosphate impairing neutrophil function, although the pathway is not fully settled. Sepsis in a neonate fed milk with liver involvement should prompt testing for galactosaemia.

### What causes cataracts in galactosaemia?

Galactitol, formed from galactose by aldose reductase in the lens, accumulates and draws water into the lens fibres. This osmotic effect produces cataract, which can develop early in life. Early withdrawal of galactose from the diet reduces the risk of cataract in galactosaemia.

### Why is a lactose-free diet used in galactosaemia?

Lactose is split into glucose and galactose, so a lactose-free diet removes the galactose load that drives toxicity. Soy or elemental formulas are used because they contain no lactose, and breast milk is stopped. The diet prevents most acute features, but long-term complications can still persist.

### Which long-term complication persists in girls despite a lactose-free diet?

Primary ovarian insufficiency is a recognised long-term complication in girls with classic galactosaemia, even with a strict diet. It can lead to delayed puberty or infertility, and hormone replacement is considered under specialist care. Speech dyspraxia and learning difficulties can also persist in galactosaemia.