[A rare D19S433*7 variant in the paternity case with mutation]

During a routine paternity casework performed with an automated genotyping using the AmpFISTR Identifiler kit, a lack of paternal allele segregation in D21S11 and off-ladder allele in D19S433 locus was observed. This raised suspicion of mutation because the other systems showed transmission of putative father's alleles to the child. To achieve the recommended value of paternity index (PI), the range of analysis was extended by additional autosomal loci (Penta D and Penta E) and haplotype of the chromosome Y. No further exclusions were observed. Additionally, a new PowerPlex ESI 17 kit was used. By comparison, the results common for both the multiplex kits confirmed the presence of the mutation in D21S11 locus. In locus D19S433, a rare variant D19S433*7 allele was evidenced in the putative father and the child. This variant allele was included in size range of allelic ladder in the PowerPlex ESI 17 kit, but not in AmpFfSTR Identifiler kit. The variant D19S433*7 allele was not reported in the Polish population before. ThlSTRe PowerPlex ESI 17 genotyping kit has two advantages, i.e. introduction of 6 loci not included in the Identifiler kit, and extended ranges of allelic ladders. It seems that a careful scrutiny of fluorescent signals following electrophoretic separation is essential to detect rare variant alleles and to avoid misinterpretation of the results.