Pathogenic variants in the MME gene cause dominant and recessive late onset axonal hereditary neuropathy. In this study, we identified that a short increase in an AT-repeat close to two MME mutations is a frequent cause of allele dropout during Sanger sequencing causing false interpretation of the results in several of the patients. This may result in an incorrect diagnosis, which has a considerable clinical impact for genetic counselling and prognosis. Although, NGS is frequently applied for routine diagnostics, Sanger sequencing is still used for verification and segregation analysis in a family. The fact that a small increase in a repetitive sequence may lead to amplification failure, is important to bear in mind when designing primers for Sanger sequencing. (By Dr. Helle Høyer, https://jmg.bmj.com/content/early/2022/03/22/jmedgenet-2021-108281 )