Tyrosinemia Type II is a rare disorder of tyrosine metabolism.


Synonyms: Richner-Hanhart syndrome (RHS), oculocutaneous tyrosinemia


Gene affected: TAT (tyrosine aminotransferase), in the liver

Gene locus: 16q22


Inheritance: autosomal recessive


Clinical features:

(1) mental retardation

(2) hyperkeratosis of the volar aspects of the hands and feet (keratosis palmaris et plantaris, palma-plantar keratoderma)

(3) thickening of the conjunctival epithelium

(4) corneal opacities (dendritic pseudokeratitis)

(5) photophobia

(6) frequent tearing


Onset is during infancy or early childhood.


Laboratory findings:

(1) increased plasma levels of tyrosine and tyrosine metabolites

(2) increased urine levels of tyrosine and tyrosine metabolites


Management includes a diet low in phenylalanine and tyrosine.


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