Immunoglobulin G subclass deficiency (IgGSCD) is a relatively common primary immunodeficiency disease (PI) in adults. The biological significance of IgGSCD in patients with chronic airway diseases is controversial. We conducted a retrospective study to characterize the clinical features of IgGSCD in this population. This study examined the medical charts from 59 adult patients with IgGSCD who had bronchial asthma or chronic obstructive pulmonary disease (COPD) from January 2007 to December 2012. Subjects were classified according to the 10 warning signs developed by the Jeffrey Modell Foundation (JMF) and divided into two patient groups: group I (n = 17) met ≥ two JMF criteria, whereas group II (n = 42) met none. IgG3 deficiency was the most common subclass deficiency (88.1%), followed by IgG4 (15.3%). The most common infectious complication was pneumonia, followed by recurrent bronchitis, and rhinosinusitis. The numbers of infections, hospitalizations, and exacerbations of asthma or COPD per year were significantly higher in group I than in group II (P < 0.001, P = 0.012, and P < 0.001, respectively). The follow-up mean forced expiratory volume (FEV1) level in group I was significantly lower than it was at baseline despite treatment of asthma or COPD (P = 0.036). In conclusion, IgGSCD is an important PI in the subset of patients with chronic airway diseases who had recurrent upper and lower respiratory infections as they presented with exacerbation-prone phenotypes, decline in lung function, and subsequently poor prognosis.
Keywords: Asthma; Chronic Obstructive Lung Diseases; IgG Subclass Deficiency; Respiratory Tract Infection.