A 3-day child vomits everything he feeds, has a distended abdomen & diarrhoea. The urine is positive for benedicts test for reducing substance. The substance in urine is –
Characteristic symptom i.e., vomiting, distended abdomen and diarrhoea along with the presence of reducing a substance in the urine suggests the diagnosis of galactosemia

Galactosemia 

Galactosemia is a group of metabolic disorders which occurs due to defect in the metabolism of galactose.
There is an inability to metabolise galactose which may be caused by a deficiency of any of the following enzymes: (1) Galactose-1 phosphate uridyl transferase (most common)


UDP-galactose-4-epimerase
Galactokinase
The defect in galactose metabolism results in accumulation of galactose-1-phosphate and galactical that are thought to have direct toxic effect on the liver and other organs.

Clinical features


Infant appears normal at birth, however, becomes symptomatic a few days to weeks after initiating galactose containing feeds.
Due to the accumulation of galactitol, damage to nerve tissue and liver occurs which causes:-


Hepatic parenchymal disease- jaundice, hepatomegaly and ascites
Mental retardation                                               
Vitreous haemorrhage 
Acidosis  
Cataract
Seizures   
Splenomegaly     
Hypoglycemia          


The accompanying GI symptoms are poor feedings, vomiting and diarrhea.
Fanconi syndrome (Aminoacidiuria, protein aria, phosphaturia) may occur.

Diagnosis

Urine shows reducing sugar which can be detected by


Benedicts reagent
Glucose oxidase method


The confirmatory diagnosis is made by the enzyme assay.
Sucrose
Glucose
Galactose
Fructose