[Defects of IgG subclasses as a cause of severe, recurrent respiratory tract infection]

IgG Immunoglobulins can be differentiated into four subclasses with different structures and functions. Partial or complete defects of one or two subclasses can be related to an impaired immune defence. We describe four children with severe recurrent bacterial airway infections. Two children had developed bronchiectasia following recurrent bronchopulmonary inflammation. Prior to diagnosis of IgG subclass deficiency other common causes of recurrent airway infections were excluded. Defects of IgG 2 or IgG 4 antibodies as well as of both classes were found with compensatory elevation of IgG 1 and IgG 3. In repeated sputum cultures haemophilus influenzae and staphylococcus aureus were isolated. This might be due to an impaired antibody production against special antigens as alpha-toxin of staphylococcus or capsular polysaccharide of haemophilus influenzae. The four cases demonstrate that in children with severe recurrent airway infections including bronchiectasia and otitis media defects of IgG subclasses have to be considered. Diagnosis should be proved by repeated determinations of blood levels after exclusion of other common causes for infections. Diminution of IgG subclasses without clinical symptoms of airway infections is also possible. If diagnosis seems to be certain intravenous substitution with 7 s gammaglobulin beside symptomatic antibiotic therapy is recommended.