(Choice A) Patients with aldolase B deficiency (hereditary fructose intolerance) cannot metabolize fructose and develop hypoglycemia, hypophosphatemia, and failure to thrive. Although reducing substances can be positive in the urine, cataracts are not present.
(Choice B) Alpha-galactosidase A deficiency (X-linked recessive) results in Fabry disease, which can present with cataracts. However, neurological findings (eg, numbness, tingling, burning pain in the hands and feet) and angiokeratomas are also characteristic.
(Choice C) Fructokinase deficiency leads to essential fructosuria, a benign condition that can result in a positive test for reducing substance but not cataracts.
(Choice E) Glucose-6-phosphatase converts glucose-6-phosphate to glucose. Glucose-6-phosphatase deficiency causes glycogen storage disease type 1 (von Gierke disease). The main clinical manifestations are hypoglycemia, lactic acidosis, hepatomegaly, and hypertriglyceridemia. Cataracts are not seen.
(Choice F) Tay-Sachs disease results from hexosaminidase A deficiency. Affected infants have retinal cherry-red spots and loss of motor skills. Cataracts are not seen.
(Choice G) Sphingomyelinase deficiency is seen in Niemann-Pick disease and leads to accumulation of sphingomyelin. Characteristics include hepatosplenomegaly, motor neuropathy, anemia, and macular cherry-red spots but not cataracts.

(Choice A) Restriction of branched-chain amino acids (eg, valine, leucine, isoleucine) is used to treat maple syrup urine disease (branched-chain alpha-ketoacid dehydrogenase deficiency) and propionic acidemia (propionyl-CoA carboxylase ).
(Choice B) Fructose and sucrose restriction is the treatment for fructose 1-phosphate aldolase (aldolase B) deficiency. This condition causes vomiting and hypoglycemia in infants after fruit or juice is introduced.
(Choice C) Galactose and lactose are excluded from the diet in patients with classic galactosemia (absent galactose-1-phosphate uridyltransferase). Galactosemia presents in neonates with jaundice, vomiting, poor feeding, lethargy, hypoglycemia, and galactose-1-phosphate accumulation.
(Choice D) Medium-chain triglycerides are restricted in medium-chain acyl-CoA dehydrogenase deficiency, a condition characterized by lethargy, seizures, and hypoketotic hypoglycemia following a period of fasting.
(Choice E) A phenylalanine-free diet is recommended in patients with phenylketonuria (phenylalanine hydroxylase deficiency). Failure to convert phenylalanine to tyrosine leads to accumulation of phenylalanine and intellectual disability if the condition is left untreated.
(Choice G) Pyridoxine (vitamin B6) can be used to treat homocystinuria, which is caused by a defect in vitamin Bedependent cystathionine synthase. This condition is characterized by elevated homocysteine levels, ectopia lentis, intellectual disability, Marfanoid body habitus, and increased occurrence of thromboembolic events.

(Choices A and D) Starch (similar to glycogen in mammals) is the major storage form of carbohydrates in plants and contains only glucose molecules. Starch consists of an unbranched portion composed of amylase and a branched portion called amylopectin. Patients with fructosemia have normal metabolism of glucose.
(Choice B) Cellulose is a linear polysaccharide of glucose that is mainly present in the cell wall of plant cells. Cellulose is an insoluble, indigestible dietary fiber that is responsible for the bulk of fecal matter.
(Choices C, E, and F) Breast milk contains the disaccharides lactose (composed of galactose and glucose) and maltose (composed of 2 glucose molecules). Patients with aldolase 8 deficiency can consume these disaccharides as their breakdown will not produce fructose. However, patients with galactosemia cannot metabolize galactose in breast milk or cow’s milk-based formula. These patients typically present in the first few days of life with jaundice, vomiting, poor feeding, and hepatomegaly.