Thrombocytopenia, or low platelet count, can run in families or be a result of some drugs and medical conditions, according to WebMD. Viral infections, including chickenpox and hepatitis C, can be causes.
Bacterial infection, blood cancer, bone marrow problems, miliary tuberculosis, and vitamin deficiencies of B12 and B9 can all result in thrombocytopenia, notes WebMD. Chemotherapy or radiation treatment on the bone marrow can affect platelet count as well. Excessive drinking of alcohol may also bring on this condition. Low blood platelet count can also occur when antibodies, which normally attack infection, destroy blood platelets instead. This condition is called idiopathic thrombocytopenic purpura.