A New Patient with Inherited TYK2 Deficiency.

Complete TYK2 deficiency (IMMUNODEFICIENCY 35 OMIM (611521)) is a rare disorder, inherited as an autosomal recessive (AR) trait, which has been previously described in nine patients from seven unrelated kindreds [[1]-[3]]. Following mandatory BCG vaccination at birth in Iran and some other countries, patients with certain inborn errors of immunity may develop BCG disease that usually appears 3 months after the vaccination [[9]-[12]]. In line with other patients with complete AR TYK2 deficiency, our patient also suffers from viral disease, particularly with herpes viruses, attributable to an impaired IFN- -mediated immunity (2, 6). Importantly, both our patient and the patient reported in 2016 by Fuchs et al. carry the same TYK2 mutation and we thus infer that our patient would show a lack of TYK2 expression despite never tested. [Extracted from the article]