Even in pneumococcal sepsis CD62L shedding on granulocytes proves to be a reliable functional test for the diagnosis of interleukin-1 receptor-associated kinase-4 deficiency.

A 9-month-old infant presented with fatal pneumococcal sepsis and attenuated inflammation indices. Even in septic conditions, flow cytometry-based CD62L shedding test on granulocytes proved to be a fast and reliable diagnostic tool for the detection of a defect in the innate immunity. Confirmatory immunologic and genetic assays identified an autosomal-recessive interleukin-1 receptor-associated kinase-4 deficiency due to compound heterozygous mutations.