Mast cell disorders including hereditary alpha-tryptasemia (HαT) and idiopathic mast cell activation syndrome (MCAS) can be associated with neurologic symptoms such as orthostatic intolerance, pain, and cognitive impairment. The origin of these symptoms is not well understood.
We aimed to characterize neurologic findings in patients with HαT and MCAS through objective measurements.
Patients with a confirmed diagnosis of HαT or MCAS with neurologic symptoms were referred for standardized autonomic testing encompassing Valsalva maneuver, deep breathing, sudomotor and tilt tests with cerebral blood flow velocity (CBFv) determination, and skin biopsies for small fiber neuropathy (SFN).
Fifteen patients with HαT (age 44.4±15.9 years), 16 with MCAS (34.4±15.5), and 14 matched controls were assessed. Baseline serum tryptase was increased in patients with HαT when compared to MCAS patients (14.3±2.5 ng/mL vs 3.8±1.8, p<0.001) and neurological symptoms were similar between the two groups. When compared to controls, orthostatic CBFv was reduced in HαT (-24.2±14.3%, p<0.001) and MCAS (20.8±5.5%, p<0.0001). Reduced nerve fibers consistent with SFN were found in 80% of HαT patients and 81% of MCAS. Mild to moderate dysautonomia was detected in all HαT and MCAS patients when results of sympathetic, parasympathetic, and sudomotor tests were combined.
We provide evidence of reduced orthostatic CBFv and SFN associated with mild to moderate autonomic dysfunction in patients with HαT and MCAS. Our findings suggest that comprehensive autonomic testing may be helpful to explain neurological symptoms and guide treatment in patients with HαT and MCAS.

Copyright © 2021. Published by Elsevier Inc.