Homing of granulocytes transfused in perineal cellulitis in a RAC2 deficiency child monitored by chimerism quantification methods.

Granulocyte transfusions can be used to treat infections when appropriate antibiotic and anti-fungal drugs have proved ineffective. We report a case of clinical efficacy of 18 granulocyte transfusions for perineal cellulitis in a 3-week-old RAC2-deficient newborn girl. This RAC2 deficiency is characterized by severe phagocyte defects including defective superoxide formation, adhesion and chemotaxis deficiency. In order to check that the granulocytes infused had reached the lesion site, the infiltration of donor cells was quantified by next generation sequencing (NGS) and digital droplet PCR after identification of DNA specific markers for donor and patient. After the 6th transfusion, 20% circulating cells and 55% cells isolated by swabbing from the lesion site were donor cells, confirming the infiltration of polynuclear cells in the perineal lesion site. These results strengthen the indication of granulocyte transfusions, and its continuation until the healing process of the skin is complete. This clinical case report highlights the potential efficacy of granulocyte transfusions to treat skin lesions in RAC2-deficient patients, a process which could be monitored by molecular biology tools for chimerism quantification.