Makiko Saitoh

Epidemiology of acute encephalopathy in Japan, with emphasis on the association of viruses and syndromes

A research committee supported by the Japanese government conducted a nationwide survey on the epidemiology of acute encephalopathy in Japan using a questionnaire. A total of 983 cases reportedly had acute encephalopathy during the past 3 years, 2007-2010. Among the pathogens of the preceding infection, influenza virus was the most common, followed by human herpesvirus-6 (HHV-6) and rotavirus. Among syndromes of acute encephalopathy, acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) was the most frequent, followed by clinically mild encephalitis/encephalopathy with a reversible splenial lesion (MERS), acute necrotizing encephalopathy (ANE) and hemorrhagic shock and encephalopathy syndrome (HSES). Influenza virus was strongly associated with ANE and MERS, HHV-6 with AESD, and rotavirus with MERS. Mortality was high in ANE and HSES, but was low in AESD, MERS and HHV-6-associated encephalopathy. Neurologic sequelae were common in AESD and ANE, but were absent in MERS.

Carnitine palmitoyl transferase II polymorphism is associated with multiple syndromes of acute encephalopathy with various infectious diseases

The high incidence of acute encephalopathy in East Asia suggests the role of genetic factors in its pathogenesis. It has recently been reported that variations of the CPT II (carnitine palmitoyl transferase II) gene may be associated with fatal or severe cases of influenza-associated encephalopathy. In the present study, we examined the genotype of CPT II in cases of acute encephalopathy associated with various preceding infections. Twenty-nine Japanese patients with acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) or acute necrotizing encephalopathy (ANE) were studied. The frequency of F352C of CPT II exon 4 was significantly higher in patients than in controls. All patients who had allele C in F352C had allele I in V368I and allele M in M647V (CIM haplotype), which reportedly decreases CPT II activity to one third of that with FIM or FVM haplotype. The frequency of CIM haplotype was significantly different between patients and controls, but not between AESD and ANE. Our results revealed that having at least one CIM allele is a risk factor for the onset of acute encephalopathy, regardless of its antecedent infections.

ADORA2A polymorphism predisposes children to encephalopathy with febrile status epilepticus.

Objective: Acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) is a childhood encephalopathy following severe febrile seizures, leaving neurologic sequelae in many patients. However, its pathogenesis remains unclear. In this study, we clarified that genetic variation in the adenosine A2A receptor (ADORA2A), whose activation is involved in excitotoxicity, may be a predisposing factor of AESD. Methods: We analyzed 4 ADORA2A single nucleotide polymorphisms in 85 patients with AESD. The mRNA expression in brain samples, mRNA and protein expression in lymphoblasts, as well as the production of cyclic adenosine monophosphate (cAMP) by lymphoblasts in response to adenosine were compared among ADORA2A diplotypes. Results: Four single nucleotide polymorphisms were completely linked, which resulted in 2 haplotypes, A and B. Haplotype A (C at rs2298383, T at rs5751876, deletion at rs35320474, and C at rs4822492) frequency in patients was significantly higher than in controls (p = 0.005). Homozygous haplotype A (AA diplotype) had a higher risk of developing AESD (odds ratio 2.32, 95% confidence interval 1.32–4.08; p = 0.003) via a recessive model. mRNA expression was significantly higher in AA than AB and BB diplotypes, both in the brain (p = 0.003 and 0.002, respectively) and lymphoblasts (p = 0.035 and 0.003, respectively). In lymphoblasts, ADORA2A protein expression (p = 0.024), as well as cellular cAMP production (p = 0.0006), was significantly higher in AA than BB diplotype. Conclusions: AA diplotype of ADORA2A is associated with AESD and may alter the intracellular adenosine/cAMP cascade, thereby promoting seizures and excitotoxic brain damage in patients.

Mutations of the SCN1A gene in acute encephalopathy

Purpose:  Acute encephalopathy is the most serious complication of pediatric viral infections, such as influenza and exanthema subitum. It occurs worldwide, but is most prevalent in East Asia. Recently, there have been sporadic case reports of epilepsy/febrile seizure and acute encephalopathy with a neuronal sodium channel alpha 1 subunit (SCN1A) mutation. To determine whether SCN1A mutations are a predisposing factor of acute encephalopathy, we sought to identify SCN1A mutations in a large case series of acute encephalopathy including various syndromes.

Acute encephalopathy with a novel point mutation in the SCN2A gene.

Mutations of the neuronal voltage-gated sodium channel alpha subunit type II (SCN2A) cause various epileptic syndromes, but have never been reported in association with acute encephalopathy. To validate the involvement of SCN2A mutations in acute encephalopathy, we screened 25 patients and found a novel missense mutation (Met1128Thr) in a patient with acute encephalitis with refractory, repetitive partial seizures (AERRPS). This finding suggests that SCN2A mutation is a predisposing factor for acute encephalopathy.

Immunomodulatory therapy in recurrent acute necrotizing encephalopathy ANE1: is it useful?

Acute Necrotizing Encephalopathy (ANE) is a rare disorder characterized by fever, seizures and rapid progression to coma after the onset of a viral infection. Most cases are sporadic, however the observation of multiple cases in the same family with recurrent episodes of ANE led to the identification of a genetic form of the disorder, called ANE1, and to the discover of the causative mutation in RANBP2 gene. We report the first Italian child with ANE1 carrying the common c.1880C>T mutation in the RANBP2 gene, who presented three episodes of acute encephalopathy in the first two years of life. The child showed a less severe clinical and neuroradiological course with respect to the previously reported patients. During the acute encephalopathy episodes he was treated with steroids and immunoglobulin. A very low steroid maintenance therapy was administered after the second episode until the onset of the third. Thirty days after the last episode he started monthly intravenous immunoglobulin that might be used for prevention of viral infections. At the moment he is still continuing a low steroid maintenance therapy and monthly IVIG. We could hypothesize that the less severe clinical presentation of the third episode might be correlated to the steroid treatment or that the patient grew older. Despite there is no evidence to support that ANE1 is an immune-mediated disease, immunomodulatory therapy might be considered in the management of ANE1 cases especially in early childhood, in which a fatal course has been frequently reported. Further studies will be necessary to define the clinical, immunological and genetic aspects, as well as the outcome of immunomodulatory therapy in patients with ANE1.

Correlation between deletion patterns of SMN and NAIP genes and the clinical features of spinal muscular atrophy in Japanese patients

We conducted molecular analysis of two candidate genes for spinal muscular atrophy (SMA), the survival motor neuron gene (SMN) and the neuronal apoptosis inhibitory protein gene (NAIP), in 16 Japanese patients with SMA and compared the phenotypic features of SMA in these patients with the corresponding genotypes. Exons 7 and/or 8 of SMN were homozygously deleted in 11 SMA type I (Werdnig‐Hoffmann disease) patients, two SMA type II patients and one SMA type III patient. Exons 5 and 6 of NAIP were homozygously deleted in six SMA type I patients. No patient had a deletion in NAIP without a deletion in SMN. Mechanical ventilation was required during the first 7 months of life in the SMA type I patients who had a deletion in both SMN and NAIP. Ventilatory support was initiated within 2 years after birth in patients who had a deletion in SMN but not in NAIP. We detected homozygous deletion of exon 5 of NAIP in the unaffected mothers of two SMA type I patients. In these families, the patients exhibited a deletion in both SMN and NAIP. The parents and unaffected siblings of these patients did not have a deletion in SMN. The present findings support the hypothesis that SMN deletion plays an important role in the development of SMA and suggest that combined deletion of both SMN and NAIP may be relevant for determining the disease severity.

Phosphatidyl ethanolamine with increased polyunsaturated fatty acids in compensation for plasmalogen defect in the Zellweger syndrome brain.

To elucidate the neuropathological mechanism of Zellweger syndrome (ZS), we studied changes in the molecular species of glycerophospholipids in the cerebral tissue by thin-layer chromatography (TLC) and fast atom bombardment mass spectrometry (FABMS). First, we estimated the amount of plasmalogens by TLC. Plasmalogen-type phosphatidyl ethanolamine (PE) accounted for 30% of the total PE in the control brain, but was absent in the ZS brain. Plasmalogen-type phosphatidyl choline (PC) was undetectable in both control and ZS brains. Next, we analyzed plasmalogen-type PE by FABMS. Oleic (18:1), arachidonic (20:4) and docosapentanoic (22:5) acids were present in the control gray matter, but not in the ZS gray matter. In compensation for the defect of plasmalogen, the level of diacyl PE with polyunsaturated fatty acids, 20:4, 22:4, 22:5 and 22:6, was higher in the ZS brain than that in the control brain. These results indicate an alteration in the molecular species of PE, which may cause abnormal neural membrane fluidity and excessive vulnerability to oxygen stress.

A case of recurrent encephalopathy with SCN2A missense mutation.

Voltage-gated sodium channels regulate neuronal excitability, as well as survival and the patterning of neuronal connectivity during development. Mutations in SCN2A, which encodes the Na(+) channel Nav1.2, cause epilepsy syndromes and predispose children to acute encephalopathy. Here, we report the case of a young male with recurrent acute encephalopathy who carried a novel missense mutation in the SCN2A gene. He was born by normal delivery and developed repetitive apneic episodes at 2days of age. Diffusion-weighted imaging revealed high-intensity areas in diffuse subcortical white matter, bilateral thalami, and basal nuclei. His symptoms improved gradually without any specific treatment, but he exhibited a motor milestone delay after the episode. At the age of 10months, he developed acute cerebellopathy associated with a respiratory syncytial viral infection. He received high-dose intravenous gammaglobulin and methylprednisolone pulse therapy and seemed to have no obvious sequelae after the episode. He then developed severe diffuse encephalopathy associated with gastroenteritis at the age of 14months. He received high-dose intravenous gammaglobulin and methylprednisolone pulse therapy but was left with severe neurological sequelae. PCR-based analysis revealed a novel de novo missense mutation, c.4979T>G (p.Leu1660Trp), in the SCN2A gene. This case suggests that SCN2A mutations might predispose children to repetitive encephalopathy with variable clinical and imaging findings.

Missense mutations in sodium channel SCN1A and SCN2A predispose children to encephalopathy with severe febrile seizures.

OBJECTIVE Acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) is a childhood encephalopathy following severe febrile seizures. The pathogenesis of AESD is considered to be fever-induced seizure susceptibility and excitotoxicity, which may be caused by sodium channel dysfunction in some cases. Here we studied whether mutations in genes encoding sodium channels, SCN1A and SCN2A, predispose children to AESD. METHODS We recruited 92 AESD patients in a nationwide survey of acute encephalopathy in Japan from 2008 to 2011. We collected their genomic DNA samples, and sequenced the entire coding region of SCN1A and SCN2A. RESULTS Five out of 92 patients (5.4%) had missense mutations either in SCN1A or SCN2A. After a preceding infection with fever, all the patients showed status epilepticus at the onset. Hemiconvulsion-hemiplegia was recognized in three patients during the acute/subacute phase. One patient had taken theophylline for the treatment of bronchial asthma just before the onset of AESD. Familial history was not remarkable except one patient with a SCN1A mutation (G1647S) whose mother had a similar episode of AESD in her childhood. A different substitution (G1674R) at the same amino acid position, as well as two other SCN1A mutations found in this study, had previously been reported in Dravet syndrome. Another SCN1A mutation (R1575C) had been detected in other types of acute encephahlitis/encephalopathy. One patient had SCN2A mutation, F328V, which had previously been reported in Dravet syndrome. Another SCN2A mutation, I172V, was novel. None of the patients were diagnosed with Dravet syndrome or genetic (generalized) epilepsy with febrile seizure plus in the following-up period. CONCLUSIONS Mutations in SCN1A and SCN2A are a predisposing factor of AESD. Altered channel activity caused by these mutations may provoke seizures and excitotoxic brain damage.