a few have not. in summary, active infection with hhv-6 is present in a substantial fraction of patients with cfs. moreover, hhv-6 is known to infect cells of the nervous system and immune system, organ systems with demonstrable abnormalities in cfs. despite this association, it remains unproven that reactivated hhv-6 infection is a cause of cfs. hashimoto's thyroiditis hashimoto's thyroiditis is the most common thyroid disease and is characterized by abundant lymphocyte infiltrate and thyroid impairment. recent research suggests a potential role for hhv-6 (possibly variant a) in the development or triggering of hashimoto's thyroiditis. pregnancy the role of hhv-6 during pregnancy leading to inflammation in the amniotic cavity has been studied. infertility hhv-6a dna was found in the endometrium of almost half of a group of infertile women, but in none of the fertile control group. natural killer cells specific for hhv-6a, and high uterine levels of certain cytokines, were also found in the endometrium of the infertile women positive for hhv-6a. the authors suggest that hhv-6a may prove to be an important factor in female infertility. cancer many human oncogenic viruses have been identified. for instance, hhv-8 is linked to kaposi's sarcoma, the epstein–barr virus to burkitt's lymphoma, and hpv to cervical cancer. in fact, the world health organization estimated (2002) that 17.8% of human cancers were caused by infection. the typical methods whereby viruses initiate oncogenesis involve suppressing the host's immune system, causing inflammation, or altering genes. hhv-6 has been detected in lymphomas, leukemias, cervical cancers, and brain tumors. various medulloblastoma cell lines as well as the cells of other brain tumors have been demonstrated to express the cd46 receptor. viral dna has also been identified in many other non-pathological brain tissues, but the levels are lower. the human p53 protein functions as a tumor suppressor. individuals who do not properly produce this protein experience a higher incidence of cancer, a phenomenon known as li-fraumeni syndrome. one of hhv-6's gene products, the u14 protein, binds p53 and incorporates it into virions. another gene product, the orf-1 protein, can also bind and inactivate p53. cells expressing the orf-1 gene have even been shown to produce fibrosarcomas when injected into mice. another product of hhv-6, the immediate early protein u95, has been shown to bind nuclear factor-kappa b. deregulation of this factor is associated with cancer. optic neuritis hhv-6 induced ocular inflammation has been reported three times. all three were reported in elderly individuals, two during 2007 and one during 2011. the first two were reported in japan and france, the most recent one in japan. these were believed to have occurred as a result of a reactivation, as anti-hhv-6 igm antibody levels were low. temporal lobe epilepsy epilepsy of the mesial temporal lobe is associated with hhv-6 infection. within this region of the brain exists three structures: the amygdala, hippocampus, and parahippocampal gyrus. mesial temporal lobe epilepsy (mtle) is the most common form of chronic epilepsy and its underlying mechanism is not fully understood. researchers consistently report having found hhv-6 dna in tissues that were removed from patients with mtle. studies have demonstrated a tendency for hhv-6 to aggregate in the temporal lobe, with the highest concentrations in astrocytes of the hippocampus. however, one group of researchers ultimately concluded that hhv-6 may not be involved in mtle related to mesial temporal sclerosis. liver failure the virus is a common cause of liver dysfunction and acute liver failure in liver transplant recipients, and has recently been linked to periportal confluent necrosis. furthermore, hhv-6 dna is often detectable only in the biopsy tissues as dna levels fall below the level of detection in blood in persistent cases. treatment there are no pharmaceuticals approved specifically for treating hhv-6 infection, although the usage of cytomegalovirus treatments (valganciclovir, ganciclovir, cidofovir, and foscarnet) have shown some success. these drugs are given with the intent of inhibiting proper dna polymerization by competing with deoxy triphosphate nucleotides or specifically inactivating viral dna polymerases. finding a treatment can be difficult when hhv-6 reactivation occurs following transplant surgery because transplant medications include immunosuppressants.