A 2-year-old girl presents with photophobia, bilateral pseudodendritic corneal lesions, palmar and plantar hyperkeratosis, and plasma tyrosine of 1800 micromol/L. Succinylacetone is absent from urine. The deficient enzyme is:

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

Explanation

Tyrosinemia type II (Richner-Hanhart syndrome) results from hepatic tyrosine aminotransferase deficiency, causing extreme tyrosine elevation. Tyrosine crystallizes in corneal epithelium producing painful pseudodendritic lesions, and causes palmoplantar keratosis and intellectual disability. Absence of succinylacetone excludes type I tyrosinemia (fumarylacetoacetate hydrolase deficiency). Tyrosinase deficiency causes albinism without hyperthyrosinemia, and HPD deficiency corresponds to type III tyrosinemia without corneal findings.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.