Cytochrome P450 (CYP) enzymes play major roles in drug metabolism. Certain single-nucleotide polymorphisms(SNPs) in CYP genes may have a large impact on CYP enzyme activity.Polymorphisms in the cytochrome P450 gene might influence blood concentration some patients have a genetic predisposition to HCQ toxicity (e.g.,from abnormalities in the ABCA4 gene)Which is not studied previously among Egyptian population