It is proposed that patients with skin disease due to presumed immunologic, genetic or viral-induced abnormalities, patients with neurological degenerations, and normal controls be evaluated with various in vitro studies of immunologic, genetic, and virologic function. This is to include studies of peripheral blood (cells and serum) as well as studies of skin obtained with a biopsy instrument. In addition, studies of gastrointestinal function will be performed where appropriate.