KIF1B and Autosomal dominant Charcot-Marie-Tooth disease type 2A1: Lastly, the phenotype associated with pathogenic variants of KIF1B, peripheral sensorimotor neuropathy named Charcot-Marie-Tooth disease type 2A1 (MIM: 118210), is highly dissimilar to speech delay; therefore, the variant in this gene was also classified as a variant of unknown significance.