TPOX Triallelic Genotype: An Interesting Pattern to Be Noted in Bone Marrow Transplantation Monitoring

TPOX triallelic genotypic pattern has been described in the setting of forensic and paternity testing but not in bone marrow transplantation (BMT) monitoring for graft engraftment.

A total of 50 cases have been studied using the AmpFLSTR(®) Identifiler™ polymerase chain reaction amplification kit as part of the workup of patients and donors before and after BMT at the American University of Beirut Medical Center.

Of the 50 studied cases, 49 showed typical allelic patterns of the variable short tandem repeats detected by the assay; however, one single patient showed a biallelic TPOX genotype in the pre-BMT specimen but a triallelic pattern in the post-BMT sample.

Triallelic patterns of TPOX should also be considered in the context of BMT monitoring testing where misinterpretation of the allelic pattern can lead to wrong unwanted conclusions related to the graft condition and proper quantification of donor DNA.