To the Editor, Mendelian susceptibility to mycobacterial disease (MSMD) is a group of primary immunodeficiencies (PIDs) characterized by increased susceptibility to mycobacteria, including weakly virulent species such as Bacille de Calmette et Guérin (BCG) vaccines and environmental mycobacteria (EM), in otherwise healthy patients with no obvious immune abnormalities [1, 2]. Fifteen genes have been described as responsible for isolated or syndromic MSMD, and all these genes encode proteins involved in the production and/or action of interferon-γ (IFN-γ)[1–3]. Complete autosomal recessive (AR) IFN-γR1 deficiency is one of the most severe forms of MSMD and is characterized by a complete lack of response to IFN-γ [1]. Patients with AR IFN-γR deficiency have high plasma IFN-γ concentrations [1, 4]. Complete AR IFN-γR1 deficiency is associated with early onset disseminated infections to mycobacteria [1, 4, 5]. Severe viral infections have also been reported in rare cases [1]. Mortality is high, as 18 of the 41 patients reported to date have died [1, 4–6]. Two different forms of complete AR IFN-γR1 deficiency exist, depending on whether or not the mutant protein is expressed [1]. Complete AR IFN-γR1 deficiency has been reported in 41 patients from 33 kindreds [1, 4–6]. In total, 32 bi-allelic mutations of IFNGR1 causing complete AR IFN-γR1 deficiency have been described [1, 4–6] including 16 singlenucleotide variants (ie, 6 missense mutations, 4 nonsense mutations, or 6 splice-site mutations), 11 small deletions, 4 small insertions [1, 4–6], and one copy number variant (CNV) corresponding to a deletion of the entire IFNGR1 gene [7].

The patient reported here (V. 1) lives in Turkey and was born to consanguineous Turkish parents in 2013 (Fig. 1a). Both the patient’s parents and his brother are healthy. The patient was vaccinated with BCG at the age of 2 months. He was hospitalized at the age of 5 months, with an ulcer at the site of BCG vaccination and a lymphadenopathy in the left axilla. Staining revealed the presence of acid-fast bacilli (AFB) in the suppurated liquid, which tested positive for M. tuberculosis complex by PCR. He was treated with isoniazid and rifampicin until the age of 10 months, when the