A 4-year-old presents with photophobia, tearing, and bilateral pseudodendritic corneal opacities along with thickened, painful plaques on the palms and soles. Plasma tyrosine is 1800 micromol/L. The deficient enzyme is:

• A Fumarylacetoacetate hydrolase
• B p-Hydroxyphenylpyruvate dioxygenase
• C Tyrosine aminotransferase ✓
• D Homogentisate oxidase

Explanation

Tyrosinemia type II (Richner-Hanhart syndrome) results from cytosolic tyrosine aminotransferase deficiency, causing marked hypertyrosinemia. Excess tyrosine crystallizes in corneal epithelium producing painful pseudodendritic keratitis, and causes palmoplantar keratosis, sometimes with intellectual disability. Fumarylacetoacetate hydrolase deficiency is type I with liver failure, p-hydroxyphenylpyruvate dioxygenase relates to nitisinone action in type I, and homogentisate oxidase deficiency is alkaptonuria.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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