1. Inherited genetic disorders, such as thalassemia and sickle cell anemia.
2. Certain medications, such as chemotherapy drugs, antiretroviral drugs, and some antibiotics.
3. Chronic diseases, such as kidney disease, HIV/AIDS, and rheumatoid arthritis.
4. Autoimmune disorders, such as lupus and rheumatoid arthritis.
5. Vitamin deficiencies, such as vitamin B12 and folate.
6. Exposure to toxins, such as lead and certain chemicals.
7. Infections, such as hepatitis and HIV.