NADPH Oxidase Subunits by Flow Cytometry in Recessive Chronic Granulomatosis Disease

Introduction Chronic granulomatous disease (CGD) is a primary immunodeficiency caused by impaired phagocytic function due to mutations in the five NADPH oxidase subunits and two other genes that are not part of this complex (gp91phox, p22phox, p47phox, p67phox, p40phox, EROS, and Rac1/2 GTP binding protein), leading to severe, recurrent bacterial and fungal infections with granuloma formation and inflammatory bowel disease-like colitis. Almost 30% of CGD result from recessive mutations. Aim Describe the utility of the quantification of NADPH oxidase subunits by flow cytometry in CGD. Case Presentation A 9-year-old girl born from non-consanguineous parents, admitted for prolonged febrile syndrome and abscessed pneumonia unresponsive to antibiotics, referred from the Hospital of Catamarca. Disseminated coccidioidomycosis was diagnosed, also based on central nervous system involvement, along with a positive PCR for coccidioidomycosis in bronchoalveolar lavage and lung biopsy. Her medical history includes hospitalizations for bilateral pneumonia due to SARS-CoV-2 and multisystem inflammatory syndrome in children with mild pericarditis at 6 years old. No family history of an inborn error of immunity. Currently waiting for hematopoietic stem cell transplantation plan. First immunology evaluation showed hypergammaglobulinemia (IgG, A, M) with normal protein response, positive autoantibodies. Normal lymphocyte subpopulations (T lymphocyte, B lymphocyte, natural killer) with high activation markers in T cells compartments (CD4+/CD8+). Increased frequencies of switched memory B lymphocyte and plasma cells. Normal lymphocyte proliferation assay with adequate TNFa production in monocytes after Bacillus Calmette–Guérin and IFNg stimulus. Normal IL-12RB1 and IFNg receptors. Complete deficiency of dihydrorhodamine oxidation with normal result for the mother. NADPH oxidase subunits by flow cytometry showed a marked decrease in gp91phox and gp67phox with normal expression of gp47phox and gp22phox. Molecular study confirmed absence of NCF2 gene transcripts. Further studies are ongoing to characterize this variant. Discussion Flow cytometry–based evaluation of NADPH oxidase components is a surrogate marker for identifying the genetic defect in CGD. This is a rapid assay for neutrophils that can be tested in any clinical laboratory.