Using singleton WES, 12 heterozygous (monoallelic) mutations in the eight MSMD-causing genes, namely TYK2, ZNFX1, IFNGR1, IL23R, JAK1, IL12B, STAT1 and IL12RB, were detected in six patients. This evidence concerns the gene TYK2 and Mendelian susceptibility to mycobacterial diseases.