Netherton syndrome (NTS) is a rare genetic skin disease caused by mutations in 
the serine protease inhibitor Kazal-type 5 gene, which encodes the 
lympho-epithelial Kazal-type-related inhibitor. NTS patients have profoundly 
impaired skin barrier function. As stratum corneum (SC) lipids have a crucial 
role in the skin barrier function, we investigated the SC lipid composition and 
organization in NTS patients. We studied the SC lipid composition by means of 
mass spectrometry, and the lipid organization was examined by infrared 
spectroscopy and X-ray diffraction. Decreased free fatty acid (FFA) chain length 
and increased levels of monounsaturated FFAs were observed in the SC of NTS 
patients compared with controls. Furthermore, the level of short-chain ceramides 
(CERs) was enhanced in NTS patients and a strong reduction in long-chain CER 
levels was seen in several patients. The changes in lipid composition modified 
the lipid organization leading to an increased disordering of the lipids 
compared with the controls. In addition, in a subgroup of patients the 
organization of the lipid layers changed dramatically. The altered FFA and CER 
profiles in NTS patients corresponded to changes in the expression of enzymes 
involved in SC lipid processing. The observed changes in lipid composition, 
lipid organization, and enzyme expression are likely to contribute to the 
barrier dysfunction in NTS.