Case Report: Pseudomonas can take a toll on a patient [version 1; peer review: 2 approved]

Pseudomonas aeruginosa (P. aeruginosa) is an aerobic Gram-negative bacterium that is implicated in the development of severe systemic infections among pediatric patients. It is identified in hospitalized chronically ill pediatric patients in association with genitourinary, respiratory tract, and skin or soft tissue infections as well as severe and life-threating infection including sepsis. A variety of immunologic mechanisms play a vital role in the host defense mechanisms against invasive infections with P. aeruginosa. Rarely, specific inborn errors of immune function are implicated in deficiencies that predispose to invasive infections with P. aeruginosa. Innate immune function including germ-line encoded pattern recognition receptors such as toll-like receptors (TLRs) and their downstream signaling is vital in the host defense against P. aeruginosa through the generation of antimicrobial peptides, cytokines/chemokines, and shaping of adaptive immune responses. Herein, we describe a previously healthy two-year-old female with an invasive skin, soft tissue, and central nervous system infection secondary to P. aeruginosa. The invasive nature of this infection prompted a careful evaluation for an inborn error of immunity. Decreased cytokine response to agonists of TLRs was documented. Targeted sequencing of interleukin-1 receptor-associated kinase (IRAK)-4 documented a homozygous deletion of exons 8-13 consistent with IRAK-4 deficiency. This report provides a vital educative message in the existing scientific literature by underscoring the importance of considering inborn errors of immunity in all patients with severe P. aeruginosa infections. Functional assessments of immune function often in combination with sequencing can accurately assign a diagnosis in a timely fashion allowing for definitive treatment and the use of necessary supportive care.