Biogenic amines derived from tryptophan in systemic and cutaneous scleroderma

Blood levels of serotonin (5-HT) and urinary excretion of 5-hydroxyindole-acetic acid (5-HIAA), tryptamine (T), and indole-acetic acid (IAA) were determined in 39 cases of systemic scleroderma and in 7 cases of very severe cutaneous scleroderma. The T/IAA ratio was normal and serotonin elevated in mild and rather severe acrosclerosis alike, i.e. in systemic scleroderma with pronounced vascular involvement. The T/IAA ratio was increased and serotonin normal in severe acroscleroderma, representing an intermediate form or transition to diffuse scleroderma, in severe diffuse scleroderma, and in severe cutaneous scleroderma. The T/IAA ratio and serotonin level were both elevated in a few cases of systemic scleroderma and in severe generalized morphea with concomitant vascular changes. The findings suggest impaired monoamine oxidase (MAO) activity in scleroderma with consequent accumulation in the organism of biogenic amines derived from tryptophan. An increased T/IAA ratio seems to be of prognostic significance in scleroderma, suggesting an adverse course of the disease.