Flushing: The most important clinical finding is flushing of the skin, usually of the head and the upper part of thorax.[6] Diarrhea: When the diarrhea is intense and explosive, it may lead to electrolyte disturbance and dehydration. Abdominal pain: Due to desmoplastic reaction of the mesentery or hepatic metastases. [citation needed] Bronchoconstriction, which may be histamine-induced, affects a smaller number of patients and often accompanies flushing. Secondary restrictive cardiomyopathy: About 50% of patients have cardiac abnormalities classically of the restrictive-type caused by serotonin-induced fibrosis of the valvular endocardium, notably the tricuspid and pulmonary valves, called cardiac fibrosis.