DHR-123 assay for evaluating NADPH oxidase functional recovery at day 100 post-HSCT in patients with chronic granulomatous disease

Abstract

Chronic granulomatous disease (CGD) is characterized by pathogenic variants in genes encoding the NADPH oxidase system, resulting in impaired phagocyte activity and increased susceptibility to infections in barrier organs and lymph nodes. Functional diagnosis is performed using the dihydrorhodamine-123 (DHR) test. Although clinical management includes antimicrobial and antifungal prophylaxis, hematopoietic stem cell transplantation (HSCT) represents the only curative therapeutic modality. This retrospective observational study evaluated the DHR test as an indicator of functional recovery of the NADPH oxidase system at D+100 post-HSCT in patients with CGD. It was based on a review of medical records from seven patients with CGD, diagnosed via the DHR test, who underwent HSCT between 2015 and 2022. Results from the DHR test and chimerism analysis performed at Day +100 post-HSCT were analyzed at a pediatric referral hospital in southern Brazil. The mean age at symptom onset was 1 year and 18 days, and the mean age at diagnosis was 4 years, 11 months, and 23 days. Five patients carried pathogenic variants in the CYBB gene. Post-HSCT, the patient exhibiting the highest ratio of median fluorescence intensity (MFI) between stimulated and unstimulated cells achieved complete chimerism; conversely, the patient with the lowest ratio displayed unsatisfactory mixed chimerism, showing no functional recovery of granulocytes. Chimerism analysis results were consistent with DHR test findings, demonstrating that patients with higher MFI ratios achieved satisfactory complete or functional mixed chimerism at D+100 post-HSCT.