PKM and pachyonychia congenita: Mechanistically, HACD2 promotes PC cells proliferation by binding to E3 ubiquitin‐protein ligase parkin (PRKN) and enhancing pyruvate kinase PKM (PKM2) dissociation from PRKN, resulting in reduced ubiquitination of PKM2 and increased dimerization of PKM2, which subsequently promote c‐Myc expression and tumor growth.