Which finding in an infant raises concern for primary immune deficiency?

The presence of recurrent deep skin abscesses in an infant is a significant indicator that may suggest a primary immune deficiency. In infants, a properly functioning immune system is crucial for fighting infections. When an infant experiences repeated episodes of skin infections, particularly those that lead to deep abscesses, it raises red flags about their immune system's ability to effectively respond to pathogens.

Primary immune deficiencies can impair different components of the immune system, leading to a heightened susceptibility to infections, including skin infections. The development of deep skin abscesses suggests that the infant is not adequately controlling bacterial infections, making this finding particularly concerning. This pattern often points to issues such as problems with antibody production, neutrophil function, or overall immune regulation, all of which could be linked to primary immune deficiencies.

In contrast, being overweight, having a single episode of a common cold, or having been treated for diarrhea do not necessarily indicate problems with the immune system. These can be common occurrences in infants and do not, by themselves, suggest underlying immunodeficiency issues. The recurrent nature of deep skin abscesses makes it a more specific and alarming sign that warrants further investigation into the infant's immune function.