Table 1 summarizes the major IDD and the methods used for their diagnosis and treatment. The clue to the diagnosis of IDD remains a high index of suspicion when one encounters a child or an adult with recurrent infections. IDD must be relatively common in Lebanon because of the high rate of interfamily marriages. With a heightened awareness and few easily available laboratory methods (underlined in table 1) the primary physician should be able to make the diagnosis of most of these diseases.