In addition to environmental factors, genetic segregation analysis provide support for the hypothesis that autosomal genes play a role in the clinical manifestation of X-ALD. Thus, in cooperation with Patrick Aubourg (INSERM U561) Hopital Saint Vincent de Paul, Paris, France) and Wolfgang Köhler (Sächsisches Landeskrankenhaus Wermsdorf, Germany) we are investigating candidate modifier genes in association studies in DNA samples of clinically very well defined X-ALD patients and controls.