Fifty-four of them suffered from indolent systemic mastocytosis, 2 had diffuse cutaneous mastocytosis, 20 had maculopapulous cutaneous mastocytosis, 2 had smoldering systemic mastocytosis, and there was a single patient with bone marrow mastocytosis. Mastocytosis patients' cognitive dysfunctions correlate with the presence of spindle-shaped mast cells in bone marrow To the Editor, Mastocytosis is a hematological neoplasm with a broad spectrum of disease caused by mast cell (MC) infiltration (i.e., impairment of function of bone marrow, liver) and degranulation (i.e., anaphylaxis).1 Recent data indicate psychological factors and neurological factors.2 Patients with mastocytosis have a significantly lower quality of life and experience increased anxiety, depression, and other symptoms such as headache or fatigue.3,4 These might be accompanied by cognitive impairment and brain fog declared by 86% of US patients, though its relation with mastocytosis and its progression hasn't been established to date.5 Some of these symptoms might result from abnormal MCs in central nervous system.6 In murine model, Esposito et al. showed that stress through corticotropin stimulates brain MCs to disrupt permeability of brain-blood barrier. [Extracted from the article]