Clinical data concerning the nature, number, and severity of clinical symptoms (as defined by the Infectious Diseases Society of America14–), age at onset of symptoms, age at diagnosis, and start of regular IV Ig replacement treatment, and the results of the latest pulmonary function tests (spirometry) and the latest high-resolution CT (HRCT) scans of the chest and abdomen were collected by a single investigator by detailed retrospective chart review and questionnaire-guided personal interview of all patients. Recurrent respiratory tract infection was defined as the occurrence of at least three episodes a year of bronchitis and/or sinusitis with a temperature of > 37.5°C. The diagnosis of bronchiectasis, splenomegaly, and lymphadenopathy was based on the findings of HRCT scans of the chest and abdomen, and the diagnosis of chronic lung disease was made when bronchiectasis was detected on chest HRCT scan and the FVC and/or FEV1 fell by at least 20% below predicted values.15 Patients with intestinal manifestations were identified as having recurrent diarrhea if they had two or more episodes a year. These patients were further evaluated for the presence of bacteria and parasites in stool, biochemical nutritional parameters (prealbumin and albumin), body mass index, GI radiographs or endoscopy, xilosa breath test, and, finally, intestinal biopsy for histology study and the study of parasites in duodenal juice. The results of the xilosa breath test and intestinal biopsy were used to establish the diagnosis of malabsorption. Chronic noninfectious diarrhea was defined as recurrent diarrhea with repeated negative stool culture findings, negative study results for parasites in duodenal juice, and evident repercussions on general status (ie, low body mass index, asthenia, and laboratory-proven malnutrition) but without demonstrable malabsorption. The definition of autoimmune disease included the following: cytopenias (idiopathic thrombocytopenic purpura, autoimmune hemolytic anemia, and leukopenia); and others (autoimmune hepatitis, rheumatoid arthritis, autoimmune thyroiditis, pernicious anemia, psoriasis, vitiligo, and alopecia areata).