Glucose-6-Phosphate Dehydrogenase Deficiency via the G6PD Gene

Glucose-6-phosphate dehydrogenase deficiency (G6PD) is a condition that mainly affects red blood cells. People with G6PD are largely asymptomatic but can develop bouts of illness. In affected individuals, mutations in the G6PD gene leads to a decrease in glucose-6-phosphate dehydrogenase enzymatic activity resulting in premature breakdown of red blood cells. Clinical features of G6PD may include hemolytic anemia leading to paleness, lumbar/substernal pain, jaundice, dark urine, fatigue, shortness of breath, and a rapid heart rate. Hemolytic anemia events are often triggered by infection or other oxidative stressors including certain drugs, medical conditions like diabetic ketoacidosis and fava beans (Rochford et al. 2013; Elyassi and Rowshan 2009; Frank 2005). Known drugs to trigger hemolysis in individuals affect with G6PD include sulfonamides, certain analgesics, naphthalene, methylene blue, thiazolesulfone, and a few non-sulfa antibiotics (nalidixic acid, dapsone, nitrofurantoin, isoniazid, and furazolidone) (Frank 2005). The World Health Organization has classified 3 main types of G6PD according to the magnitude of G6PD enzyme deficiency with class I being most severe with less than 10% of normal enzymatic function. Preventative measures such as blood transfusions, splenectomy, folic acid supplementation, and avoidance of drugs or foods that cause hemolysis have been used in management of G6PD (Frank 2005).

G6PD is inherited in an X-linked recessive manner and thereby primarily affects males. Heterozygous females are usually asymptomatic. It affects an estimated 400 million people worldwide with the highest prevalence reported in Africa, southern Europe, the Middle East, Southeast Asia, and the Pacific islands. Missense mutations in the G6PD gene predominantly affect protein stability and are the main documented causative mutation type (Villiamy et al. 1988; Cappellini and Fiorelli 2008). Each ethnic group has predominant founder mutations such as G6PD Mediterranean (c.563C>T). G6PD deficiency provides protection against malarial infection owning to its prevalence in the indicated populations. G6PD enzyme catalyzes the first step in the pentose phosphate pathway which produces antioxidants to protect cells against oxidative stress. Triggers that heighten oxidative stress in red blood cells result in hemolytic anemia and symptom onset in patients with G6PD (Frank 2005).

Sequencing by this method is capable of detecting >95% of causative mutations for the G6PD. For individuals with biochemical testing indicating G6PD deficiency, clinical sensitivity is predicted to be >95%.

This test provides full coverage of all coding exons of the G6PD gene, plus ~10 bases of flanking noncoding DNA. We define full coverage as >20X NGS reads or Sanger sequencing.