Mast cells are considered sensors of environmental and emotional stress, exist in all body parts and are related to the pathway from stress to inflammation. Mastocytosis defines a rare disease characterized by the accumulation of abnormal mast cells in multiple organs. Here, we present a 77-year-old woman with a background of aggressive systemic mastocytosis who developed impaired cognition, depression, anxiety, visual hallucinations, delusions, and insomnia. Symptoms alleviated only after initiating midostaurin, a tyrosine kinase inhibitor. Systemic mastocytosis should be kept in mind when visual hallucinations are concomitant with chronic or recurrent multi-system disturbances and do not benefit from treatment as usual.