The telltale sniffles. Ear infections. Sore throats. Picking up an ailment at school is practically a rite of passage for children nowadays. But it's important that you don't simply brush off these recurring illnesses as normal childhood health problems. A serious underlying disease might be to blame. Primary Immunodeficiency, or PI, is a genetic defect that can compromise a child's immune system, leading to an increased susceptibility to certain infectious illnesses. There are more than 100 types of PI; each has somewhat different symptoms, depending on which parts of the immune system are affected. Some deficiencies are deadly, while others are mild. In children with PI, usual childhood illnesses occur frequently and can drag on and become chronic despite the use of antibiotics. If a child suffers from eight or more ear infections or two or more serious sinus infections within a year, he or she could have an underlying PI. Other warning signs are failure to gain weight or grow normally and a family history of PI. While there are more than 1 million children and young adults in the United States affected by PI, experts estimate that 50 percent to 70 percent of those with the disease go undiagnosed. Without diagnosis and treatment, constant infections can significantly weaken your child's immune system. Parents should know that a simple and inexpensive blood test could identify the disorder in more than 95 percent of cases. Once diagnosed, there are several treatment options that can provide a better quality of life or, in some cases, a cure. The Jeffrey Modell Foundation, a nonprofit research foundation devoted to the study of PI, is making a profound difference in many lives by raising awareness of the disease. In January 2005, as a result of a national public awareness and physician education campaign, 34 Jeffrey Modell Diagnostic and Referral Centers throughout the United States reported promising figures. They calculated an increase of 52 percent in the number of newly diagnosed patients and a 45 percent increase in the number of patients receiving treatment.