Individuals will be excluded from this protocol if they already have a diagnosis, if their previous evaluations leave no clue to pursue, if they appear to have a known diagnosis that has not been made, or if their subjective complaints far exceed any objective findings. We will not admit patients under one month of age to this protocol. This exclusion occurs because there is no urgency for a very early diagnosis and care is more readily proffered to older individuals at the Clinical Center. Patients under one year of age will be admitted only if they are medically stable and require admission to the Clinical Center for diagnosis.