[Could it be an immune defect? Background and diagnosis].

With modern immunological and molecular biological laboratory techniques, some 100 primary immunodeficiencies can now be diagnosed and differentiated. The importance of diagnosing a primary immunodeficiency (PID) as early as possible cannot be overemphasized. In patients with PID, recurrent infections can lead to permanent damage and sometimes even to death. On the occasion of a first visit to the physician, the patient usually presents with nonspecific symptoms, in particular recurrent infections, a challenging situation in terms of making the correct diagnosis. Relevant warning signals and a possible family history should also prompt at least such simple laboratory tests as a blood differential and the quantitative determination of immunoglobulins, followed where necessary by more specific evaluations. Early treatment, for example, with immunoglobulins may enable many patients to lead a virtually normal life, and in some cases bone marrow transplantation or gene therapy may even result in a cure.