Among nine transglutaminases identified in human skin, transglutaminases 1, 3, and 5 are involved in cornified envelope formation [87], as shown in acral peeling skin syndrome mediated via missence mutations in transglutaminase 5 [88] and lamellar ichthyosis in transglutaminase 1 deficiency [89,90]. Here, TGM1 is linked to lamellar ichthyosis.