Genetic testing surprisingly revealed pathogenic homozygous variants in <i>IL12RB1</i> Exon 9, c.913A>T (p. Lys305*) in both the patient and his father, with a completely healthy asymptomatic carrier mother who is not blood related to the patient's father.<h4>Conclusion</h4>It is challenging to diagnose MSMD, especially in developing countries where health systems are poor and have limited resources. The gene discussed is IL12RB1; the disease is Mendelian susceptibility to mycobacterial diseases.