Abnormal DHR is not always synonymous with a diagnosis of chronic granulomatous disease.

Myeloperoxidase (MPO) deficiency is a rare inherited neutrophil disorder associated with an increased risk of infections. We present a case of a male child with no underlying medical conditions who presented with a difficult-to-manage renal abscess, enterococcal urosepsis and an abnormal dihydro-rhodamine 123 test. On genetic evaluation, he was found to have a homozygous mutation in the MPO gene, leading to the diagnosis of MPO deficiency. This case highlights the clinical importance of MPO activity in the clearance of specific microorganisms. MPO deficiency should be considered in the differential diagnosis of paediatric patients with difficult-to-manage abscesses.