[Idiopathic mast cell activation syndrome].

Background: Idiopathic mast cell activation syndrome (MCAS) is one of the causes for recurrent complaints. The diagnosis is sometimes delayed but also often made incorrectly.
Case: Our patient presented with recurrent attacks of itching, redness of the skin, diarrhea and near collapse. During an attack his serum tryptase level rose significantly. We could not identify an underlying trigger. A diagnosis of idiopathic mast cell activation syndrome was made. He was successfully treated with a combination of H1 and H2 blockade.
Conclusion: MCAS is characterized by recurrent complaints. To make the diagnosis a significant rise in mast cell mediators is required. Given the diversity of symptoms many patients with somatically unexplained symptoms wrongfully believe to be suffering from MCAS.