PNPLA1 (patatin-like phospholipase domain-containing protein 1) is a specialized transacylase enzyme that catalyzes the final step in omega-O-acylceramide (acylceramide) biosynthesis, which is essential for epidermal barrier function 12. The enzyme transfers linoleic acid from triglycerides to omega-hydroxyceramides, producing acylceramides that are critical components of the stratum corneum's lipid lamellae and cornified lipid envelope 13. PNPLA1 shows selective incorporation of linoleic acid over other fatty acids in this transacylation reaction 3. The enzyme requires proper localization to lipid droplets through interaction with the co-activator ABHD5 for optimal function 4. Loss-of-function mutations in PNPLA1 cause autosomal recessive congenital ichthyosis (ARCI) in both humans and dogs, characterized by defective acylceramide synthesis, impaired skin barrier function, and severe scaling 156. Studies have identified numerous pathogenic mutations that either completely abolish enzyme activity or disrupt its subcellular localization to lipid droplets 5. The conservation of PNPLA1 function across mammalian species underscores its fundamental importance in epidermal lipid metabolism and skin barrier maintenance 1.