 All patients or another respondent for the patient will fill out a questionnaire including demographic information age, gender, race, ethnic group, education level, state of residence, current symptoms, medications, medical history, and history of possible exposures to toxins or viruses. A second questionnaire, which includes questions related to mental health, sexual behavior, alcohol and drug use, is optional for participants age 21 and older. These questionnaires are designed to uncover features of hepatitis-associated aplastic anemia and possibly reveal a common cause of the disease. 