G6PD Potenza: A Novel Pathogenic Variant Broadening the Mutational Landscape in the Italian Population

<b>Background:</b> Glucose 6 phosphate dehydrogenase (<i>G6PD)</i> is a rate-limiting enzyme of the pentose phosphate pathway. The loss of <i>G6PD</i> activity in red blood cells increases the risk of acute haemolytic anaemia under oxidative stress induced by infections, some medications, or fava beans. More than 200 single missense mutations are known in the <i>G6PD</i> gene. A 41-year-old woman with a family history of favism coming from the Basilicata region (Italy) was evaluated at our hospital for <i>G6PD</i> abnormalities. <b>Methods:</b> DNA was extracted from a peripheral blood sample and genotyped for the most common <i>G6PD</i> pathogenic variants (PVs). Positive results obtained by Restriction Fragment Length Polymorphism (<i>RFLP</i>), as per practice in our laboratory, were then reconfirmed in Sanger sequencing. <b>Results:</b><i>RFLP</i> analysis highlighted a variant compatible with the <i>G6PD Cassano</i> variant. Confirmatory testing by Sanger unexpectedly identified a novel variant: c.1357G>A, p.(Val453Met) (NM_001360016.2); the same variant was found in the patient's mother. In silico models predicted a deleterious effect of this variant at the protein level. The novel <i>G6PD</i> variant was named "<i>G6PD Potenza</i>" on the basis of the patient's regional origin. <b>Conclusions:</b> This case describes a novel <i>G6PD</i> variant. It also highlights how the Sanger sequencing technique still represents an indispensable confirmatory standard method for variants that could be misinterpreted by only using a "first-level" approach, such as the <i>RFLP</i>. We stress that the evaluation of clinical manifestations in G6PD-deficient patients is of primary importance for the classification of each new <i>G6PD</i> mutation, in agreement with the new WHO guidelines.