Clinical correlates of blood serotonin levels in patients with mastocytosis

Background Mastocytosis is a clonal disorder associated with an increased mast cell burden. We have recently demonstrated the ability of human mast cells to express and be activated through multiple serotonin receptors; to synthesize and release serotonin; and that mastocytosis patients may have abnormal serotonin levels. As serotonin has been implicated in the genesis of clinical symptoms found in association with some chronic diseases, we have now determined the whole blood serotonin levels in 29 patients diagnosed with mastocytosis, and correlated these levels with multiple clinical and laboratory parameters. Materials and methods Patients with mastocytosis were categorized according to disease variant. Blood serotonin values were determined and correlated with values reported for normal subjects; and clinical and laboratory features of the disease. Results Total blood serotonin levels followed a bimodal distribution in line with our earlier report,unlike the normal distribution reported for normal individuals. Serotonin levels did not correlate with platelet numbers, liver function tests or serum tryptase levels. Patients with lower serotonin values had greater rates of fatigue (P = 0·0001), migraine headaches (P = 0·0028), psychiatric symptoms (P = 0·0001), diarrhoea (P = 0·0407), flushing (0·0085), and abdominal and bone pain (P = 0·0001). Conclusions Our study suggests that low blood serotonin levels help define a sub‐group of patients with mastocytosis that are more likely to present with neurological and gastrointestinal complaints, and suggests that the use of pharmacologic agents that alter blood serotonin levels could be explored in selected patients.