Tryptophan metabolism "via" nicotimic acid in patients with scleroderma

The tryptophan metabolism "via" kynurenine was studied in five patients with scleroderma after aminoacid loading. Four of these patients had abnormal tryptophan metabolism, characterized by a large urinary excretion of kynurenine and kynurenic acid in two cases, of kynurenine, 3-hydroxykynurenine and kynurenic acid in one case and of 3-hydroxyanthranilic acid in another case and generally a reduced excretion of xanthurenic acid and its 8-methyl ether in comparison with a group of healthy controls. Only two of the four patients had a normal response to tryptophan loading after pyridoxine administration, while no one of these responded to nicotinamide supplementation. But the simultaneous administration of pyridoxine and nicotinamide to three of these patients normalized the excretory picture after tryptophan loading. This suggested the presence of a combined vitamin deficiency in seleroderma. As four out of five patients showed total excretory values of kynurenine, kynurenic acid and acetylkynurenine higher than that of the controls, the sum of these values might be considered as a characteristic index of scleroderma.