- Gene expression of enzymes for tryptophan degradation pathway is upregulated in the skin lesions of patients with atopic dermatitis or psoriasis. Ito, M., Ogawa, K., Takeuchi, K., Nakada, A., Heishi, M., Suto, H., Mitsuishi, K., Sugita, Y., Ogawa, H., Ra, C. J. Dermatol. Sci. (2004)