Plasma histamine elevation in a large cohort of sickle cell disease patients.

The role of mast cells has been questioned in sickle cell disease (SCD). We performed a prospective study evaluating plasma histamine and tryptase levels in a cohort of paediatric and adult patients, in steady state (n = 132) and during vaso-occlusive crisis (VOC) (n = 121). Histamine level was elevated in 18% of patients in steady state and in 61% during VOC. Median histamine level was significantly higher during VOC than in steady state (24·1 [7·0-45·0] vs 9·6 [6·2-14·4] nmol/l, P < 0·0001). Tryptase level was slightly increased during VOC without reaching pathological values. These results suggest a role of mast cell activation in SCD pathophysiology.