What is a characteristic symptom of carcinoid syndrome?

Facial flushing is a characteristic symptom of carcinoid syndrome, which is primarily associated with carcinoid tumors that typically arise in the gastrointestinal tract but can metastasize to the liver and other locations. The flushing is attributed to the overproduction of serotonin and other vasoactive substances by the carcinoid tumors. When these substances enter the systemic circulation, they cause vasodilation, leading to sudden episodes of flushing, often on the face and neck. This symptom is distinct and often serves as an important clinical indicator of the presence of carcinoid syndrome.

Other symptoms, such as continuous coughing, severe headaches, and joint pain, do not specifically align with carcinoid syndrome and can arise from other conditions, thus they lack the specific association seen with facial flushing in this context.