A common reason for bringing an infant or child for a medical visit is recurrent infections. This may refer to infections that are too great in number, too severe, or too long lasting; that are associated with unusual complications; or that fail to resolve with standard therapy. The causes are multiple and can be grouped into four categories: the normal child, the child with atopic disease, the child with another chronic condition, and the child with an immunodeficiency.
The approach to the child with recurrent infections will be reviewed here. Laboratory studies evaluating the function of the immune system and specific immunodeficiencies are discussed briefly here and in more detail elsewhere. (See "Laboratory evaluation of the immune system" and "Primary humoral immune deficiencies: An overview" and "Selective IgA deficiency: Clinical manifestations, pathophysiology, and diagnosis" and "Severe combined immunodeficiency (SCID): An overview" and "Primary disorders of phagocytic function: An overview" and "Clinical manifestations, epidemiology, and diagnosis of common variable immunodeficiency in adults" and "Syndromic immunodeficiencies" and "Inherited disorders of the complement system".)
The goal of this diagnostic approach is to differentiate the child with a primary immunodeficiency from the normal child who had more than the average number of viral infections or the child who has an underlying disease that mimics infection, predisposes the child to certain types of infections, and/or results in secondary immune system dysfunction. Most often these categories can be determined from the history, physical examination, and screening investigations.
Recurrent infections are infections that are too great in number, too severe, or too long lasting. Recurrent infections are defined as two or more severe infections in one year, three or more respiratory infections (eg, sinusitis, otitis, bronchitis) in one year, or the need for antibiotics for two months/year. Severe/serious infections include those with persistent fever or confinement to bed for a week or more, failure to respond to oral antibiotics and/or the need for intravenous antibiotics or hospitalization, infections with an unusual pathogen, unusual complications (eg mastoiditis, pleural effusion, abscesses), or persistent laboratory abnormalities (eg, leukocytosis, elevated ESR/CRP, persistent imaging abnormalities).
Clinical features suggestive of a primary immunodeficiency — The following features should lead to suspicion of an immunodeficiency and consideration of referral to an immunology specialist for evaluation [1-7]: