ABSTRACT
Upper and lower respiratory infections are among the most commonly encountered illnesses seen by primary care physicians and subspecialists including allergy/immunologists, pulmonologists, and otolaryngologists. While treatment of uncomplicated sinusitis, otitis media, bronchitis, and pneumonia is straightforward, recurrent or refractory infection challenges the physician to recognize and identify underlying conditions predisposing to infection. A broad range of risk factors may contribute to recurrent or relapsing infection, including anatomical derangements, aeroallergen hypersensitivity, cigarette smoke exposure, cystic fibrosis, antibiotic resistance, and immunodeficiency disorders. Numerous underlying systemic disorders such as sickle cell disease, viral infections, splenectomy, malnutrition, cirrhosis, diabetes mellitus, renal failure, and alcoholism can cause variable degrees of secondary immune impairment. In addition to classic immunosuppressive medications, drugs such as parenteral gold, prednisone, and phenytoin can cause immunoglobulin abnormalities (see Table 1).
