IT HAS been known for many years that the urine Ehrlich reaction is strongly positive in cases of acute porphyria. This was generally interpreted as due to excessive urobilinogen until 1931, when Paula Sachs1 clearly distinguished this substance from the Ehrlich-reacting chromogen in porphyria urines. She based the distinction on differences in solubility and the failure of the porphyria chromogen upon oxidation to exhibit green fluorescence with zinc acetate. Rather, it was oxidized to a brown pigment differing from urobilin and believed to represent what the older literature had rather vaguely designated as "urofuscin." Waldenström2 spoke of this as the "red pigment," and still later Waldenström and Vahlquist3 studied the chromogen in more detail, confirming the observation that, unlike urobilinogen, it is not extracted from urine by most organic solvents. They noted that the Ehrlich aldehyde compound, in addition to the strong absorption band at 550 to
WATSON CJ. SOME STUDIES OF NATURE AND CLINICAL SIGNIFICANCE OF PORPHOBILINOGEN. AMA Arch Intern Med. 1954;93(5):643–657. doi:10.1001/archinte.1954.00240290001001
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