Many investigators have endeavored laboriously to discover the pathogenesis of diffuse collagen disease morphologically, chemically, and immunologically, but the common denominator of collagen disease has not been found.
With regard to intermediary metabolism of phenylalanine and tyrosine, essential amino acids, there remains much to be confirmed, but the schema prepared by Neubauer1,2 from his experimental results of the urine of alkaptonurics is generally considered to represent their normal metabolic pathway. The diseases considered to be due to blocks of the intermediary metabolism of phenylalanine and tyrosine are phenylketonuria, albinism, tyrosinosis, and alkaptonuria. All of these diseases arise from a rare and inherent defect (Fig. 1).
Moreover, Levine, Marples, and Gordon3,4 and Levine, Dann, and Marples5 demonstrated, in a course of studies of premature infants receiving a diet of relatively high-protein-content cow's milk (5 gm. or more per kilogram per day),
NISHIMURA N, YASUI M, OKAMOTO H, KANAZAWA M, KOTAKE Y, SHIBATA Y. Intermediary Metabolism of Phenylalanine and Tyrosine in Diffuse Collagen DiseasesI. The Presence of 2,5-Dihydroxyphenylpyruvic Acid in the Urine of Patients with Collagen Disease. AMA Arch Derm. 1958;77(3):255–262. doi:10.1001/archderm.1958.01560030001001
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