Which condition presents with cataracts due to galactitol accumulation and has a milder phenotype?

Which condition presents with cataracts due to galactitol accumulation and has a milder phenotype?

• A. Galactokinase deficiency
• B. Classic galactosemia
• C. Fructokinase deficiency
• D. Aldolase B deficiency

Answer: (A)

When galactose cannot be processed properly at the first step of its metabolism, it is shunted into the aldose reductase pathway and converted to galactitol. Galactitol accumulates in the lens because it is osmotically active and poorly cleared, causing lens swelling and cataract formation. This mechanism explains why the phenotype is milder: the problem is isolated to galactitol buildup in the eye, without the widespread toxicity seen in more severe forms of galactose metabolism disorders that affect the liver, kidneys, and brain. Among the options, the condition that presents with cataracts from galactitol accumulation and a milder overall presentation is galactokinase deficiency. In classic galactosemia, the defect is in a later step (galactose-1-phosphate uridyltransferase), leading to serious neonatal illness with liver disease and failure to thrive. Fructokinase deficiency causes essential fructosuria, which is usually benign and lacks cataracts. Aldolase B deficiency causes hereditary fructose intolerance with hypoglycemia and liver symptoms, not cataracts.

When galactose cannot be processed properly at the first step of its metabolism, it is shunted into the aldose reductase pathway and converted to galactitol. Galactitol accumulates in the lens because it is osmotically active and poorly cleared, causing lens swelling and cataract formation. This mechanism explains why the phenotype is milder: the problem is isolated to galactitol buildup in the eye, without the widespread toxicity seen in more severe forms of galactose metabolism disorders that affect the liver, kidneys, and brain.

Among the options, the condition that presents with cataracts from galactitol accumulation and a milder overall presentation is galactokinase deficiency. In classic galactosemia, the defect is in a later step (galactose-1-phosphate uridyltransferase), leading to serious neonatal illness with liver disease and failure to thrive. Fructokinase deficiency causes essential fructosuria, which is usually benign and lacks cataracts. Aldolase B deficiency causes hereditary fructose intolerance with hypoglycemia and liver symptoms, not cataracts.