Disorders in the metabolism of tyrosine are observed in the inborn metabolic anomaly, alkaptonuria, and in so-called tyrosinosis. In the latter condition, tyrosine, dihydroxyphenylalanine, hydroxyphenylpyruvic acid and hydroxyphenyl acetic acid appear in the urine.1 Tyrosine is occasionally found in the urine in cases of cystinuria.2 tyrosinuria may also occur independently of any anomaly of metabolism. The substance has been recovered in crystalline form from the urine of a normal subject3 and in various pathologic conditions, mainly involving the liver and biliary passages.4 The unreliability of the crystalloscopic method of diagnosis was emphasized in a previous communication.5
Frerichs and Städeler,6 who first demonstrated the presence of leucine and tyrosine in the urine of a patient with acute yellow atrophy of the liver, established the basis for the belief that the amino-acids excreted in the urine in this disease are derived from the decomposition of the liver proteins. In view of the