TYROSINOSIS is a hereditary disorder characterized by cirrhosis, severe hypophosphatemic rickets, renal tubular defects, and derangement in tyrosine metabolism, now a well-established clinical entity. The main metabolic features of this disorder are elevated serum tyrosine and increased excretion of p-hydroxyphenylpyruvic acid (pHPPA), p-hydroxyphenylacetic acid (pHPAA), and p-hydroxyphenyllactic acid (pHPLA). These metabolic products point to a block of the pHPPA-oxidase. In liver specimens from patients with tyrosinosis Sakai and Kitagawa,1 Gentz et al,2 and Taniguchi and Gjessing3 found no activity of this enzyme. Whether this block is due to a genetically determined lack of this enzyme;2 multiple enzymatic defects which include this enzyme; or3 a secondary inhibition of the enzyme due to some other hereditary metabolic defect is unknown. The term tyrosinosis, first used by Medes,4 is used to describe the condition.
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