Familial fructokinase deficiency causes no symptoms because:
**Core Concept**
Familial fructokinase deficiency is a rare genetic disorder caused by mutations in the FKBP15 gene, leading to a deficiency of the enzyme fructokinase. This enzyme is responsible for phosphorylating fructose to form fructose-1-phosphate in the liver.
**Why the Correct Answer is Right**
Fructokinase deficiency leads to an accumulation of fructose in the liver, but this accumulation is not toxic to the cells because the liver also expresses a second enzyme, aldolase B, which can phosphorylate fructose to form fructose-1-phosphate. The presence of aldolase B ensures that the fructose can still be metabolized, thereby preventing any adverse effects.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the deficiency of fructokinase alone does not prevent the accumulation of fructose in the liver.
* **Option B:** This option is incorrect because the liver's ability to metabolize fructose is not impaired in familial fructokinase deficiency.
* **Option C:** This option is incorrect because the symptoms of familial fructokinase deficiency are not related to the accumulation of fructose in the liver.
**Clinical Pearl / High-Yield Fact**
Familial fructokinase deficiency is a rare genetic disorder, but it is an important example of how the body can compensate for enzyme deficiencies through the presence of alternative pathways.
**Correct Answer:** C.