Mendelian susceptibility to mycobacterial disease is a rare syndrome that predisposes to poor virulent mycobacteria and environmental nontuberculous mycobacteria. Also, severe infection with salmonella nontifoid are seen in this syndrome. Th e most common complaints of these patients are widespread lymphadenopathy. Our four cases are common features of lymphadenopathy. Four month old cases are twin brothers. Both were admitted with generalized lymphadenopathy and persistent symptoms of oral moniliazis. Ten years old man who is the third case of salmonella infection, was admitted with complaints of bloody diarrhea and generalized lymphadenopathy. Our fourth eleven years old male patient with salmonella infection, was admitted with persistent oral moniliazis and lymphadenitis due to a history of appendectomy. IL-12Rβ1 defect should be kept in mind in the diff erential diagnosis of patients with chronic lymphadenopathy.