Abstract
Chronic granulomatous disease (CGD) is a rare immunodeficiency disorder characterized by life threatening infections. It results from mutations in any of the four genes CYBB (gp91phox), CYBA (p22phox), NCF-1(p47phox), and NCF-2 (p67phox). The aim of this study was to characterize the molecular basis of CGD in Omani patients. CGD was suspected in 13 patients from 8 families by clinical examination and investigated biochemically (Nitroblue tetrazolium test), and by flowcytometry Dihydrorhodamine test (DHR). Using direct DNA sequencing, GeneScan and allele-specific PCR technologies we analyzed the genetic variations of NCF-1 complex comprising functional and pseudogenes. Only one patient presented Xlinked inheritance pattern, who incidentally also had McLeods Syndrome. He was demonstrated to have a large deletion of approximately 600 kb involving both CYBB gene and the McLeods gene (XK). Amongst the remaining 12 patients of autosomal recessive transmission, we were able to identify mutations in the NCF-1 gene, (the most common form of autosomal recessive CGD) in 6 patients. In four kindred from one family we found the homozygous G784A mutation (Gly262Ser) in Exon 8 of the NCF-1 gene. Additionally, two patients had homozygous ?GT mutations in the functional NCF-1 gene. Thus, amongst 8 families studied, we were able to identify the underlying molecular basis of CGD in four (54%). Despite extensive analysis of all the four major genes of the NADPH-oxidase, we could not define the molecular basis of CGD in 6 patients from the remaining 4 families. The study must be extended towards the analysis of two other genes namely (NCF-4 and Rap1A) in order to decipher the causal locus and associated mutations.