Papillon-Lefèvre syndrome (PLS) is an uncommon disease. Less than 300 cases have been described. PLS is characterized by the association between palmar plantar hyperkeratosis (PPK) and severe precocious periodontitis that results in the premature loss of both the primary and secondary dentitions. It is known that periodontitis (PE), the destructive phase of periodontal disease, is a multifactor phenomenon involving a variety of molecular species, among them free radicals and reactive oxygen species (ROS). Antioxidants have been shown to play a critical role in modulating ROS-induced damages during PE. We wondered if patients belonging to a family group with different grades of PLS severity may present altered plasma concentrations of oxidation products as well as of lipophilic antioxidants, like Coenzyme Q or vitamin E, which are molecules that possess well-known antioxidant properties and could play a role in PE processes. We also wondered about the actual plasma total antioxidant capacity of these subjects as well as a complete identification of their plasma fatty acids features, which have been never investigated before. The results we obtained indicate an impairment in the antioxidant capacity of the subjects characterized by abnormally high hydroperoxide levels and, in some cases, by altered CoQ and vitamin E contents. Moreover, an essential fatty acid deficiency (EFAD) was registered on the basis of the peculiar plasma fatty acid patterns found (i.e. low PUFA, high MUFA and high delta-9 desaturase activity). This finding would support the hypothesisby Gutteridge and co-workers (Free Radic. Res. 1998, 28: 109-114) that conditions exist in which some forms of oxidative stress can lead to changes characteristic of EFAD.