## **Core Concept**
Tyrosinemia type II, also known as Richner-Hanhart syndrome, is a rare genetic disorder caused by a deficiency of a specific enzyme involved in the metabolism of the amino acid tyrosine. This condition leads to elevated levels of tyrosine in the blood and urine, causing various clinical manifestations.

## **Why the Correct Answer is Right**
The correct answer, **Tyrosine aminotransferase**, is the enzyme whose deficiency leads to Tyrosinemia type II. Tyrosine aminotransferase is crucial in the first step of tyrosine catabolism, converting tyrosine into p-hydroxyphenylpyruvate. A deficiency in this enzyme results in the accumulation of tyrosine and its metabolites, leading to the clinical features observed in Tyrosinemia type II, such as intellectual disability, growth retardation, and eye, skin, and mucous membrane lesions.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not correspond to the enzyme deficient in Tyrosinemia type II.
- **Option B:** This option is incorrect as it refers to a different enzyme, fumarylacetoacetate hydrolase, which is deficient in Tyrosinemia type I, a more severe form of the disease.
- **Option D:** This option is incorrect because it does not accurately represent the enzyme deficient in Tyrosinemia type II.

## **Clinical Pearl / High-Yield Fact**
A key clinical feature of Tyrosinemia type II is the presence of **ocular, cutaneous, and oral lesions**, along with neurological symptoms. Early diagnosis and dietary restriction of tyrosine can significantly improve outcomes. This condition highlights the importance of amino acid metabolism in preventing neurological and systemic damage.

## **Correct Answer:** C. Tyrosine aminotransferase.