A 3-year-old complains of painful eyes with photophobia. Examination shows bilateral dendritic corneal ulcers and thickened hyperkeratotic plaques on the palms and soles. Plasma tyrosine is markedly elevated. Which enzyme deficiency explains this presentation?

• A Phenylalanine hydroxylase
• B Fumarylacetoacetate hydrolase
• C Homogentisate oxidase
• D Tyrosine aminotransferase ✓

Explanation

Oculocutaneous tyrosinemia type II (Richner-Hanhart syndrome) results from hepatic tyrosine aminotransferase deficiency. Excess tyrosine crystallizes in corneal epithelium causing painful keratitis, and causes palmoplantar keratosis plus intellectual disability. Fumarylacetoacetate hydrolase deficiency is tyrosinemia type I, which causes liver failure rather than corneal lesions, killing option B.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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