Abnormal melt curve profile during prothrombin 20210G → A analysis due to the 20209C → T variant

The common factor II 20210G → A mutation, located in the 3′-untranslated region, is an important risk factor for the development of thromboembolic disorders, especially in Caucasians. A number of methods are employed for clinical laboratory diagnosis of this mutation, some of which are capable of detecting adjacent 3′-end sequence variations. We present results from an African deep vein thrombosis patient tested for the 20210G → A mutation by real-time polymerase chain reaction and melt-curve analysis using hybridization probes that incidentally detected an adjacent 3′-untranslated region variant. The patient sample was tested using the Factor II (Prothromobin) G20210A Kit (Roche Diagnostics, Indianapolis, Indiana, USA), in conjunction with the Roche LightCycler. A polymerase chain reaction fragment from the 3′-end of the F2 gene was subsequently sequenced for identification of the variant. Melt-curve analysis revealed a normal 20210*G peak and an unknown aberrant allelic peak. Following sequence analysis, the patient was determined to be heterozygous for 20209C → T. The presence of the 20209C → T variant in the current patient and in eight other reported individuals of African descent, most with thrombosis-associated complaints, suggests that this rare variant poses a potential increased risk for thromboembolic disease in this ethnic group.