ClinVar

Description

The N171K variant has been published previously in association with pachyonychia congenita (Wilson et al., 2011; Lin et al., 19999; Smith et al., 2001; Smith et al., 2005). It was not observed in approximately 6,500 individuals of European and African American ancestry in the NHLBI Exome Sequencing Project, indicating it is not a common benign variant in these populations. N171K is a semi-conservative amino acid substitution, which may impact secondary protein structure as these residues differ in some properties. This substitution occurs within a known mutational hotspot region (helix initiation motif) that is highly conserved across all species and among all members of the keratin family. Many other pathogenic variants in patients with pachyonychia congenita have been reported at the same codon (N171Y,/T/S/D) and in nearby residues (Q166P, I167S/N, L170F, F174V, ) according to the Human Gene Mutation Database (Stenson et al., 2014). It is well established that keratin gene mutations affecting the residues at the ends of the central rod domains of the keratin proteins (helix initiation and termination motifs) interfere with proper keratin intermediate filament assembly and function, resulting in hyperkeratosis (Chamcheu et al., 2011). Therefore, we consider N171K to be pathogenic.