Bilateral optic neuropathy and unilateral tonic pupil associated with acute human herpesvirus 6 infection: a case report
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- Oberacher-Velten, I.M., Jonas, J.B., Jünemann, A. et al. Graefe's Arch Clin Exp Ophthalmol (2005) 243: 175. doi:10.1007/s00417-004-0986-8
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Human herpesvirus 6 (HHV-6), a widespread virus and causative agent of exanthema subitum in children, has been associated with a number of neurologic disorders including cranial nerve palsies, seizures, encephalitis, meningitis, and multiple sclerosis.
A 31-year-old man presented with bilateral optic neuropathy, disc edema, and unilateral tonic pupil, which were found to be associated with acute HHV-6 infection. The patient had been suffering from juvenile diabetes for 5 years. One week after onset of intravenous antiviral therapy with foscarnet, disc edema subsided, and tonic pupil reaction was no longer detectable.
HHV-6 infection may play a role as a causative agent in patients with optic neuropathy and tonic pupil.
KeywordsHuman herpesvirus 6Optic neuropathyDisc edemaTonic pupil
HHV-6 is a T-lymphotropic herpesvirus, which infects almost all children by the age of 2 years and persists lifelong . Prospective studies have shown that HHV-6 is the most common pathogen responsible for febrile illness in infants and in some infants is associated with febrile convulsions . Two distinct variants of HHV-6—HHV-6A and HHV-6B—have been described, the B subtype commonly being responsible for primary infection in infants [3, 6]. Primary infection in healthy adults is rare. Reactivation of HHV-6 is especially found in the immunocompromised, causing serious illnesses . We report on a patient with bilateral optic neuropathy/disc edema and unilateral tonic pupil associated with acute HHV-6 infection.
A number of studies have suggested that the central nervous system can be a site for persistent HHV-6 infection [1, 3, 4, 6, 7]. Challoner et al.  described plaque-associated expression of HHV-6 in multiple sclerosis. Donati et al.  found significantly elevated levels of HHV-6 in surgical brain resections of patients with mesial temporal lobe epilepsy. HHV-6 was localized to hippocampal and temporal lobe astrocytes.
Regarding disorders of the eye, the orbit, and the cranial nerves supplying the (extra-)ocular muscles, HHV-6 has been associated with primary ocular lymphoma  and trochlear palsy . Qavi et al.  found HHV-6 to be capable of infecting corneal epithelial cells in vitro causing morphological changes similar to those caused by other human herpesviruses. HHV-6 antigens were found in retinas of patients with acquired immune deficiency syndrome (AIDS) with and without AIDS-associated retinitis . Fillet et al.  found HHV-6 infection in retinas with AIDS-associated retinitis but not in HIV-seropositive patients with normal fundus examination or in HIV-seronegative patients.
In the patient presented, acute HHV-6 infection was associated with optic neuropathy, disc edema, and tonic pupil. IgM antibodies against HHV-6 were found on repeated examinations in serum samples. The virus could not be detected in cerebrospinal fluid, blood, or bone marrow by polymerase chain reaction. This is consistent with localized reactivation of HHV-6 in the young patient, who is supposed to be immunocompromised by his juvenile diabetes. One might argue that the disc edema and tonic pupil could have been caused by the diabetes. However, no other signs of diabetic retinopathy (microaneurysms, intraretinal hemorrhages, cotton wool spots, intraretinal microvascular abnormalities) could be found. Donati et al.  found HHV-6 to be localized to astrocytes in patients with mesial temporal-lobe epilepsy. Based on this localization to astrocytes, one might conjecture that the optic nerve is one of the sites of HHV-6 infection. Further studies including histological investigations are needed to evaluate the role of HHV-6 in disorders of the optic nerve and orbit, which has therapeutic consequences.