Chronic Granulomatous Disease: Clinical and Molecular Characterization of Brazilian Patients

Chronic granulomatous disease (CGD) is a rare inborn error of immunity caused by defects in components of the NADPH oxidase that impair the elimination of infectious microorganisms. Individuals affected by CGD become more susceptible to recurrent and severe infections. Six male patients from Southern Brazil were clinically and genetically analyzed through data collection from medical records and massively parallel sequencing by a panel for the following genes: CYBB, CYBA, NCF1, NCF2, and NCF4 and whole genome sequencing analysis. The gene-scan technique was used to identify the GT deletion in NCF1. The most common affected organs were the lungs, skin, and lymph nodes; the most common clinical manifestations were recurrent pneumonia, cutaneous involvement, lymph node manifestations, and failure to thrive. Four patients were identified with variants in CYBB: p.Cys257Ser, which is novel; p.Cys257Arg; p.Arg157Ter; and p.Trp483Ter. Both missense variants damage the loop E in gp91^phox, a region with functional and structural relevance for the protein. Functional studies show the expression absence of the protein in patients with the variant p.Arg157Ter. The variant p.Trp483Ter is predicted to undergo nonsense mRNA-mediated decay. The GT deletion in NCF1 was identified in two siblings from consanguineous parents: one homozygous and the other apparently heterozygous for the deletion, both with a clinical diagnosis of CGD. Variant analysis in this gene is particularly challenging due to the presence of pseudogenes. A hypothesis for this genotypic discrepancy is the occurrence of a second type of pseudogene lacking the GT deletion, which may have arisen in one parent and been transmitted to the patient observed as heterozygous, being misinterpreted in the analyses as a functional NCF1 sequence.