Gain-of-function STAT1 mutations are associated with intracranial aneurysms

•Aneurysms are an integral part of the disease.•Regular imaging to screen for aneurysms and vasculitis is highly recommended.•Higher reactivity in phosphorylating STAT4 may implicate a role in the development of autoimmunity.•Increased TGF-β type 2 receptor expression and higher phosphorylation rate of SMAD3 may indicate increased TGF-β signaling in.•GOF STAT1 mutations are probably associated with Mendelian susceptibility to mycobacterial disease.

Chronic mucocutaneous candidiasis, characterized by persistent or recurrent fungal infections, represents the clinical hallmark in gain-of-function (GOF) signal transducer and activator of transcription 1 (STAT1) mutation carriers. Several cases of intracranial aneurysms have been reported in patients with GOF STAT1 mutation but the paucity of reported cases likely suggested this association still as serendipity. In order to endorse this association, we link the development of intracranial aneurysms with STAT1 GOF mutation by presenting the two different cases of a patient and her mother, and demonstrate upregulated phosphorylated STAT4 and IL-12 receptor β1 upon stimulation in patient's blood cells. We also detected increased transforming growth factor (TGF)-β type 2 receptor expression, particularly in CD14+ cells, and a slightly higher phosphorylation rate of SMAD3. In addition, the mother of the patient developed disseminated bacille Calmette-Guérin disease after vaccination, speculating that GOF STAT1 mutations may confer a predisposition to weakly virulent mycobacteria.