CDK4 and pachyonychia congenita: Given the upregulation of CDK4/6 and mTOR signaling shown in gene analysis of PC, inhibition of PC by CDK4/6 inhibitor in xenograft models, and increase in sensitivity of PC to CDK4/6 inhibition by mTOR inhibitors, there is a strong rationale to combine CDK4/6 and mTOR inhibitors in PC treatment.