LQCL2605 - CMLE - Two Peaks in the DHR Flow Cytometry Test for Chronic Granulomatous Disease: X-Linked Carrier or Post-Transplant Patient?-LQCL2605

LQCL2605 - Educational Activity

Pdf Summary

This Clinical Immunology LabQ module reviews chronic granulomatous disease (CGD) and the use of dihydrorhodamine-123 (DHR-123) flow cytometry to diagnose CGD and monitor donor engraftment after hematopoietic stem cell transplantation (HSCT). CGD is a rare inborn error of immunity caused by defects in the NADPH oxidase complex (most commonly X-linked CYBB/gp91phox, with other autosomal recessive gene causes such as NCF2), leading to impaired reactive oxygen species generation and poor intracellular killing of pathogens. Patients are predisposed to severe, recurrent, often catalase-positive bacterial and fungal infections—frequently involving lungs, skin/abscesses, lymph nodes, liver, and sometimes bone—with organisms such as Staphylococcus aureus and Aspergillus species being prominent.<br /><br />The module contrasts chimerism testing methods used post-transplant (STR analysis, RT-PCR targeting SNPs/InDels, and NGS), noting that these molecular methods require DNA extraction and can have longer turnaround times. It emphasizes that DHR-123 testing can also assess post-HSCT chimerism functionally by measuring neutrophil oxidative burst and calculating the neutrophil oxidative index (NOI). Two distinct neutrophil populations (one normal, one abnormal) may indicate either an X-linked female carrier state (due to random X inactivation) or, importantly, a post-HSCT CGD patient with mixed donor/recipient neutrophils from delayed engraftment or graft decline. Reporting should include both NOI values and the proportions of normal vs abnormal populations, with the percent normal neutrophils serving as an estimate of donor chimerism.<br /><br />A case illustrates a male CGD patient post-HSCT whose DHR showed two peaks and ~87% functional (donor) neutrophils at day 103 despite earlier >95% donor chimerism by RT-PCR. STR testing confirmed the decline, prompting closer monitoring. The patient developed transient renal dysfunction and viral infections (BK, EBV, parainfluenza), after which chimerism improved to full engraftment by day 220. The module concludes that DHR-123 is a rapid, cost-effective tool for monitoring engraftment in CGD, helping detect complications and guide clinical decisions.

Keywords

chronic granulomatous disease (CGD)

dihydrorhodamine-123 (DHR-123) flow cytometry

NADPH oxidase complex defects

CYBB/gp91phox X-linked CGD

NCF2 autosomal recessive CGD

neutrophil oxidative burst assay

neutrophil oxidative index (NOI)

hematopoietic stem cell transplantation (HSCT) engraftment monitoring

mixed chimerism donor/recipient neutrophils

catalase-positive infections (Staphylococcus aureus, Aspergillus)