Immunodeficiency is a common thought among both patients and physicians when confronted with what is perceived as an excessive number, duration, or severity of infections. Because of this, the starting point for evaluating patients for suspected immunodeficiency is based on what constitutes “too many infections.” It generally is agreed that children with normal immune systems may have an average of 6 to 8 respiratory tract infections per year for the first decade of life. Even after a pattern of abnormal infection is established, questions of secondary immunodeficiency should first be raised. The relatively uncommon primary immunodeficiency diseases are statistically dwarfed by secondary causes of recurrent infection, such as malnutrition, respiratory allergy, chronic cardiovascular, pulmonary, and renal disease, and environmental factors. On the other hand, a dizzying spiral of progress in our understanding of the genetics and immunology of primary immunodeficiency disease has resulted in improved diagnostic and therapeutic tools. Twenty-five newly recognized immunologic disease genes have been cloned in the last 5 years.<sup>24 Puck J.M. Primary Immunodeficiency Diseases JAMA 1997 ;  278 : 1835

Cliccare qui per andare alla sezione Riferimenti</sup> It has become arguably more important than ever for us to recognize the clinical and laboratory features of these relatively uncommon, but increasingly treatable, disorders.