Reduced impact of viral load of HHV-6 in liquor on severity of AESD due to exanthema subitum: A case report and literature review.

BACKGROUND: The most common causative pathogen of acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) was reported as HHV-6. Although excitotoxic injury with delayed neuronal death is considered to be a possible pathogenesis of AESD, the detailed pathophysiology remains unclear. CASE PRESENTATION: We present a twelve-month-old girl with AESD due to HHV-6 primary infection. She was successfully treated for AESD including targeted temperature management and the administration of vitamin B1, B6, and L-carnitine. Although the viral load of HHV-6 in her liquor was high (12,000 copies/mL), she fully recovered without antiviral agent use. DISCUSSION: There has been no study focusing on the HHV-6 viral load in patients with AESD, and only a few case reports have been published. We reviewed the clinical features and viral load in the liquor of our case and four reported infants with AESD due to HHV-6 primary infection who had real-time PCR tests results. Viral loads in the three patients with a poor prognosis were 31.5, negative, and 3,390 copies/mL, respectively. On the other hand, the copy numbers of HHV-6 DNA in the two patients with no sequelae were 12,000 and 106 copies/mL, respectively, and our case had the highest viral load among the five summarized patients.

HHV-6: an unusual cause of cerebellar ataxia.

Human herpesvirus 6 (HHV-6) infection is the cause of roseola infantum in children. The reactivation of HHV-6 is associated with multiple clinical syndromes including encephalitis and myelitis, especially in haematopoietic stem cell transplant recipients. However, the virus can cause encephalitis in other immunosuppressed as well as immunocompetent individuals. We report a case of a 70-year-old woman who was immunocompromised secondary to treatment of rheumatoid arthritis with leflunomide and methotrexate. The patient presented with acute ataxia, diplopia and dysarthria. MRI brain showed an enhancing lesion in the midbrain. The diagnosis of HHV-6 encephalitis was made after HHV-6 A DNA was detected in both serum and cerebrospinal fluid. Treatment consisted of a 3-week course of intravenous ganciclovir along with physiotherapy. At a 3-month follow-up, repeat MRI brain showed a decrease in size and oedema of the lesion and the patient's neurological function was improved.

Brainstem infarction associated with HHV-6 infection in an infant.

INTRODUCTION: The relevant literature includes several case reports on cerebral infarction in children with HHV-6 infection; however, there is no report of brain stem infarction. CASE: An 11-month-old girl was hospitalized because of fever. She was unable to stand up and meet her mother's gaze. Magnetic resonance imaging (MRI) indicated a right pons and mid-brain lesion; a diagnosis of brainstem infarction was made. After her fever subsided, a rash developed on her trunk and limbs; blood examination results indicated a primary HHV-6 infection. She was treated with aspirin, edaravone, and mannitol to prevent further complications. At the age of 18months, the auditory brainstem response (ABR) was unremarkable and she is developing well. DISCUSSION AND CONCLUSION: A limited number of studies have reported HHV-6 infection-associated infarction, and no cases of brainstem infarction have been reported. One possible cause of cerebral infarction is antiphospholipid antibody syndrome (APS) triggered by the infection. HHV-6 may also directly infect vascular endothelial cells and cause angiopathy. However, the real mechanism of infarction remains unclear. Our patient had a favorable prognosis despite brainstem infarction.

Successful treatment and FDG-PET/CT monitoring of HHV-6 encephalitis in a non-neutropenic patient: case report and literature review.

Human herpesvirus (HHV)-6 reactivation is associated with severe forms of encephalitis among patients undergoing hematopoietic stem cell transplantation. Cases in non-neutropenic patients are uncommon. The efficacy of ganciclovir and other compounds that are used for the treatment of HHV-6 encephalitis remains suboptimal and linked to toxicity. Valganciclovir, the oral prodrug of ganciclovir, could be practical to treat outpatients, but it is not commonly used for severe cases. We report a case of HHV-6 encephalitis in a non-neutropenic patient successfully treated with valganciclovir and undergoing therapeutic drug monitoring in plasma and in the cerebrospinal fluid. Resolution of infectious foci was documented by cerebral MRI and F18-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT). A review of the literature on HHV-6 encephalitis is also reported.

Clinically mild infantile encephalopathy associated with excitotoxicity.

Acute infectious encephalopathy is very frequently observed in children in East Asia including Japan. Acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) is the most common subtype in Japan; however, more than 40% of the patients remain unclassified into specific syndromes. To investigate the underlying pathomechanism in those with unclassified acute encephalopathy, we evaluated brain metabolism by MR spectroscopy. Among 20 patients with acute encephalopathy admitted to our hospital during January 2015 to May 2016, 12 could not be classified into specific syndromes. MR spectroscopy was performed in 8 of these 12 patients with unclassified encephalopathy. MR spectroscopy showed an increase of glutamine with a normal N-acetyl aspartate level on days 3 to 8 in three of the 8 patients, which had normalized by follow-up studies. The three patients clinically recovered completely. This study suggests that excitotoxicity may be the underlying pathomechanism in some patients with unclassified mild encephalopathy.

Hippocampal signal abnormality on the first day of illness in acute encephalopathy with biphasic seizures and late reduced diffusion caused by HHV-6 infection.

We report a 13-month-old girl who developed acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) with transient reduced diffusion in the hippocampus and anterior commissure on diffusion-weighted imaging (DWI), which was performed on the first day after febrile status epilepticus (FSE) as the initial neurological symptom of AESD. DWI just after late seizures showed high signal intensity lesions in both left hippocampus and anterior commissure, and left extratemporal and occipital subcortical white matter. HHV-6 DNA was positive in both blood and cerebrospinal fluid samples. DWI at two months after onset showed atrophy in the left mesial temporal lobe and extratemporal and occipital lobe without the signal abnormalities. Although it has been reported that magnetic resonance images tend to show no acute abnormality during the first two days in typical AESD, transient reduced diffusion could be found on the DWI performed on the first day of AESD.

Human herpesvirus-6 encephalitis after allogeneic hematopoietic cell transplantation: what we do and do not know.

Human herpesvirus-6 (HHV-6) encephalitis following allogeneic hematopoietic cell transplantation is a serious and often fatal complication accompanying reactivation of HHV-6B. Incidence varies among studies, but is reportedly 0-11.6% after bone marrow or PBSC transplantation and 4.9-21.4% after umbilical cord blood transplantation, typically around 2-6 weeks post transplant. Symptoms are characterized by memory loss, loss of consciousness and seizures. Magnetic resonance imaging (MRI) typically shows bilateral signal abnormalities in the limbic system. This complication is considered to represent acute encephalitis caused by direct virally induced damage to the central nervous system, but our understanding of the etiologies and pathogenesis is still limited. The mortality rate attributable to this pathology remains high, and survivors are often left with serious sequelae such as impaired memory and epilepsy. Despite the poor prognosis, no validated treatments or preventative measures have been established. Establishment of preventative strategies represents an important challenge. This article reviews the current knowledge of the clinical features, incidence, pathogenesis and treatment of HHV-6 encephalitis, and discusses issues needing clarification in the future to overcome this serious complication.

Sequential FDG PET and MRI findings in a case of human herpes virus 6 limbic encephalitis.

A 50-year-old woman developed a human herpes virus 6 limbic encephalitis characterized by memory loss and somnolence, 3 weeks after a cord blood-derived stem cell transplantation. Sequential scalp electroencephalogram failed to detect seizure activity. Cerebrospinal fluid polymerase chain reaction assay demonstrated human herpes virus 6 deoxyribonucleic acid (positive, 3.74 log). Acute phase FDG PET imaging showed bilateral intense FDG uptake in both hippocampi and amygdalae. After antiviral treatment (gancyclovir followed by foscarnet), neurologic symptoms disappear gradually. Late phase FDG PET imaging showed a regression in FDG uptake representing hippocampal hypometabolism because of hippocampal sclerosis.

Human herpesvirus 6 encephalopathy predominantly affecting the frontal lobes.

Isolated cases of human herpesvirus 6 encephalopathy have recently been reported, although the pathophysiology remains largely unknown. To elucidate the changes specific to human herpesvirus 6 encephalopathy on diagnostic images, this study investigated magnetic resonance imaging findings in 10 patients with a diagnosis of human herpesvirus 6 encephalopathy including diffusion-weighted imaging in 6 of 10, and findings of cerebral blood flow imaging by single-photon emission computed tomography in 9 of 10 patients. No abnormalities were evident on T(1)-weighted, T(2)-weighted, or fluid-attenuated inversion-recovery magnetic resonance imaging during acute phases; however, diffusion-weighted imaging indicated abnormal hyperintensity in the subcortical white matter of the frontal lobes in all six patients during the acute phase. Cerebral blood flow single-photon emission computed tomography revealed decreased perfusion, predominantly in the frontal region of all nine patients during their clinical course. Disturbances predominantly affecting the frontal lobes (region) on magnetic resonance imaging and cerebral blood flow single-photon emission computed tomography were common in all patients, suggesting that the findings may be characteristic of human herpesvirus 6 encephalopathy.

Human herpesvirus 6 meningoencephalitis in allogeneic hematopoietic stem cell transplant recipients.

We retrospectively investigated the clinical characteristics of human herpesvirus 6 (HHV-6) meningoencephalitis within 100 days after allogeneic hematopoietic stem cell transplantation (HSCT). Of 1148 patients who received transplants between January 1999 and December 2003, 11 patients (0.96%) with HHV-6 meningoencephalitis were identified. Ten of 11 recipients received hematopoietic stem cells from donors other than HLA-identical siblings. Confusion was the most frequent central nervous system (CNS) symptom, and a skin rash with high-grade fever preceded the CNS symptoms in 9 patients. Magnetic resonance imaging of the brain showed an abnormal increased T2 signal in the hypothalamus of 5 patients. Eight patients were treated with ganciclovir, and an improvement of CNS symptoms was obtained in 3 patients; 3 patients treated with acyclovir showed no improvement. Improvement in the meningoencephalitis seemed less frequent in patients with abnormal findings in the hypothalamus than in those without such findings. Because the symptoms of HHV-6 meningoencephalitis mimicked those of cyclosporine- or tacrolimus-induced encephalopathy, the drugs were withdrawn at the onset of CNS symptoms in 10 patients, resulting in the development of grade IV graft-versus-host disease (GVHD) in 5 patients. Three patients died of HHV-6 meningoencephalitis, and 6 died of other causes, including GVHD. In conclusion, HHV-6 meningoencephalitis is a rare but potentially life-threatening complication in patients who undergo allogeneic HSCT. Careful assessment of the clinical findings and the brain may allow early and precise diagnosis of HHV-6 meningoencephalitis and contribute to improving its prognosis.

Case report: primary infection by human herpesvirus 6 variant a with the onset of myelitis.

A case of primary infection by human herpesvirus 6 (HHV-6) variant A in a 54-year-old woman, which occurred at the same time as the onset of encephalomyelitis, is reported. The correlation between the two events is discussed. It is speculated that, during the early phase of the infection, the HHV-6 spread to the central nervous system and triggered a pathogenic process that initially developed without symptoms. When the neurological disorders appeared, HHV-6 had already established a latent state: only the virus carried by infected blood cells was detected in the cerebrospinal fluid.

Acute necrotizing encephalopathy associated with human herpesvirus-6 infection.

An extremely rare case of acute necrotizing encephalopathy caused by human herpesvirus-6 variant type B infection is reported. The patient, a 14-month-old previously healthy female, presented with high fever and generalized tonic convulsion followed by rapid deterioration of consciousness. On the second day of the illness, the protein level of the cerebrospinal fluid increased without pleocytosis. On the third day, magnetic resonance images demonstrated symmetric, abnormal signal intensity lesions in the bilateral thalamus, cerebellum, and brainstem. On the fourth day, characteristic maculopapular rash of exanthema subitum appeared on the trunk. Human herpesvirus-6 deoxyribonucleic acid was detected by the polymerase chain reaction in the serum, and immunoglobulin G and immunoglobulin M of serum human herpesvirus-6 were positive. On the twelfth day of illness, the patient died as a result of severe brain damage. Acute necrotizing encephalopathy should be included in the differential diagnosis when examining infants and young children with fulminating consciousness disturbance and intractable convulsion. In addition, as a causative virus, human herpesvirus-6 has to be considered at the pre-eruptive stage of exanthema subitum. Magnetic resonance images are useful because they reveal the characteristic distribution of lesions specific to acute necrotizing encephalopathy.