The spectrum of infectious pathogens in patients with primary or secondary immunodeficiency

Many non-infectious diseases have as a common complication the secondary development of infections, which are most likely to occur in immunocompromised individuals. Immunodeficiency (ID) is classified into primary and secondary ID (SID). Primary ID results from fundamental defects in proteins and cells that are critical for specific immune responses. Extrinsic factors, such as long-term use of immunosuppressive drugs and chronic diseases, can also affect immune responses, leading to a state of SID. In this review, we summarized the spectra of potential infectious pathogens in primary and SID, which are very different from those in immunocompetent individuals. We hope that this review will help clinicians with empirical management of infections in immunocompromised individuals caused by different etiologies and lead to better patient outcomes.