This study will collect samples of blood, stool, bone marrow, or other tissues from patients with hepatitis-associated aplastic anemia to investigate a possible association between exposure to viruses and the development of aplastic anemia in these patients. Cells from the samples obtained may be grown in the laboratory for future studies. Patients' samples may be used to:

• Study abnormalities that occur in hepatitis-associated aplastic anemia;
• Test for various viruses;
• Test immune function;
• Measure factors related to the patients' disease or diseases they may be at risk for;
• Evaluate the effectiveness of current therapies, refine treatment approaches, and identify potential new therapies;
• Identify possible measures for disease prevention;
• Identify possible genetic factors associated with hepatitis-associated aplastic anemia.

Patients 2 years of age and older with severe aplastic anemia that developed within 6 months of an episode of hepatitis may be eligible for this study.

Participants will complete questionnaires and provide tissue samples as described below.

Questionnaires

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.

Sample Collections

• Blood- will be collected at the time of the patient's initial evaluation or upon enrollment into the study and possibly periodically during the study. Blood will be drawn through a needle in an arm vein.
• Bone marrow- may be collected as part of the patient's standard medical care or specifically for research purposes of this study. For this procedure, the skin over the hipbone and the outer surface of the bone itself are numbed with an injection of a local anesthesia. Then, a larger needle is inserted into the hipbone and marrow is drawn into a syringe. Marrow cells are suctioned two to six times during the 15-minute procedure.
• Stool- will be provided by the patient.

Liver- tissue may be biopsied as part of the patient's general medical care or for NIH patients, as part of their enrollment in a treatment protocol.