Hiroko Ikeda

HLA-B locus in Japanese patients with anti-epileptics and allopurinol-related Stevens-Johnson syndrome and toxic epidermal necrolysis.

INTRODUCTION Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are rare but life-threatening severe cutaneous adverse reactions. Recently, strong associations of HLA-B*1502 and HLA-B*5801 with carbamazepine- and allopurinol-induced severe cutaneous adverse reactions were found in Han Chinese patients, respectively, but ethnic differences in the associations have been reported. The objective of this study is to clarify the involvement of HLA-B*1502 and HLA-B*5801 in Japanese SJS/TEN patients. METHODS HLA-B genotyping was performed on 58 Japanese SJS/TEN patients between July 2006 and April 2008 from multicenters in Japan. RESULTS There were no HLA-B*1502 carriers among 58 SJS/TEN patients. This patient group included seven carbamazepine-related and 11 aromatic anti-epileptic agent-related SJS/TEN patients. In addition, there were five HLA-B*5801 carriers, which included four allopurinol-related SJS/TEN patients. CONCLUSION While HLA-B*1502 is unlikely to be associated with carbamazepine-related or aromatic anti-epileptic agent-related SJS/TEN, HLA-B*5801 was significantly associated with allopurinol-related SJS/TEN in Japanese.

HLA-B*1511 is a risk factor for carbamazepine-induced Stevens-Johnson syndrome and toxic epidermal necrolysis in Japanese patients

Stevens‐Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are rare but life‐threatening severe cutaneous adverse reactions. Recently, strong associations of HLA‐B*1502 with carbamazepine‐induced SJS/TEN have been found in Han Chinese patients. These associations have been confirmed in several Asian populations, excluding Japanese. SJS patients carrying HLA‐B*1508, HLA‐B*1511, or HLA‐B*1521, which are members of the HLA‐B75 type along with HLA‐B*1502, were detected in studies in India and Thailand. In the current study, we genotyped the HLA‐B locus from 14 Japanese typical and atypical SJS/TEN patients in whom carbamazepine was considered to be involved in the onset of adverse reactions. Although there were no HLA‐B*1502 carriers, four patients had HLA‐B*1511. Our data suggest that HLA‐B*1511, a member of HLA‐B75, is a risk factor for carbamazepine‐induced SJS/TEN in Japanese.

HLA Class I markers in Japanese patients with carbamazepine‐induced cutaneous adverse reactions

Carbamazepine (CBZ) is frequently used for treating epilepsy, but this drug causes cutaneous adverse drug reactions (cADRs) that may range from mild to severe. It is reported recently that the human leukocyte antigen HLA‐B*1502 is associated with Stevens‐Johnson syndrome (SJS) induced by CBZ in Han Chinese. We examined HLA class I in 15 Japanese patients who fulfilled the diagnostic criteria for CBZ‐induced cADRs (mild in 10 and severe = SJS in 5). HLA‐B*1518, HLA‐B*5901 and HLA‐C*0704 alleles showed higher relative risks (above 10.0) for severe cADRs. The haplotype (HLA‐A*2402‐B*5901‐C*0102) had high relative risk (16.09) for severe cADRs. In patients with severe cADRs, frequencies of HLA‐A*1101, HLA‐A*3303, HLA‐B*1501, HLA‐B*4403, HLA‐B*5101, HLA‐B*5201, HLA‐C*0702, and HLA‐C*1202 alleles are relatively lower than in the Japanese population. These data may suggest that HLA‐B*5901 is one of the candidate markers for CBZ‐induced SJS in Japanese.

STXBP1 mutations cause not only Ohtahara syndrome but also West syndrome—Result of Japanese cohort study

We performed STXBP1 mutation analyses in 86 patients with various types of epilepsies, including 10 patients with OS, 43 with West syndrome, 2 with Lennox‐Gastaut syndrome, 12 with symptomatic generalized epilepsy, 14 with symptomatic partial epilepsy, and 5 with other undetermined types of epilepsy. In all patients, the etiology was unknown, but ARX and CDKL5 mutations were negative in all cases. All coding exons of STXBP1 were analyzed by direct‐sequencing. Two de novo nucleotide alterations of STXBP1 were identified in two patients with Ohtahara and West syndrome, respectively. No de novo or deleterious mutations in STXBP1 were found in the remaining 84 patients with various types of symptomatic epilepsies. This is the first case report showing that STXBP1 mutations caused West syndrome from the onset of epilepsy. STXBP1 analysis should be considered as an etiology of symptomatic West syndrome without explainable cause.

CDKL5 alterations lead to early epileptic encephalopathy in both genders

Purpose:  Genetic mutations of the cyclin‐dependent kinase‐like 5 gene (CDKL5) have been reported in patients with epileptic encephalopathy, which is characterized by intractable seizures and severe‐to‐profound developmental delay. We investigated the clinical relevance of CDKL5 alterations in both genders.

PCDH19-related female-limited epilepsy: Further details regarding early clinical features and therapeutic efficacy

Abnormalities in the protocadherin 19 (PCDH19) gene cause early-onset epilepsy exclusively in females. We aimed to explore the genetic and clinical characteristics of PCDH19-related epilepsy by focusing on its early features and treatment efficacy. PCDH19 was analyzed in 159 Japanese female patients with early-onset epilepsy via direct sequencing and multiplex ligation-dependent probe amplification (MLPA) analysis. We identified 17 patients with PCDH19 abnormalities: point mutations were observed in 14 patients and whole PCDH19 deletions were detected in 3 patients. One affected sister of a proband with a mild phenotype was also analyzed. The frequency of PCDH19 deletion among all probands identified in Japan was 12.5% (3/24, including 7 probands reported previously by us). Clinical features included early onset (mean age at onset, 8.6 months), recurrent clusters of brief seizures (17/18), fever sensitivity (18/18), tonic seizures (13/18, probably including focal tonic seizures), tonic-clonic seizures (8/18), focal seizures often with subsequent generalization (17/18), intellectual disabilities (15/18), and autistic traits (13/18). Three patients exhibited delay in motor milestones before seizure onset. In 16 patients, seizures appeared in clusters from the onset of the disease. Among 6 patients for whom detailed information at onset was available, 2 onset patterns were identified: a biphasic course of short seizure clusters (each within days) in 2 patients and a prolonged course of clusters (from weeks to a month) in 4 patients. In both cases, initial seizures started during fever and transiently disappeared with the decline of fever; however, afebrile clusters recurred. In the former patients, motor development was delayed before onset, and seizures appeared in strong clusters from the onset of the disease. In the latter patients, initial development was normal and initial seizures were mild, but were followed by strong clusters lasting several weeks, even without fever. Treatment using phenytoin, potassium bromide, and clobazam showed high efficacy. Although focal seizures were the main feature in PCDH19-epilepsy, the efficacy of carbamazepine was poor. This study highlighted the significance of PCDH19 deletion, a unique pattern of initial seizure clusters, and the efficacy of antiepileptic drugs. Our data will facilitate early diagnosis and development of a treatment strategy for better clinical management of patients with PCDH19-related epilepsy.

Specific HLA types are associated with antiepileptic drug-induced Stevens-Johnson syndrome and toxic epidermal necrolysis in Japanese subjects.

AIM This preliminary study investigated genomic biomarkers for Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), related to three antiepileptic drugs, zonisamide, phenobarbital and phenytoin. PATIENTS & METHODS HLA class I and HLA-DRB1 loci were genotyped for Japanese patients with zonisamide-, phenobarbital- or phenytoin-induced SJS/TEN (n = 12, 8 and 9, respectively) and for healthy Japanese volunteers (n = 2878). RESULTS Carrier frequencies of HLA-A*02:07 in patients with zonisamide-induced SJS/TEN and in the general Japanese population were 41.7 and 6.81%, respectively. Carrier frequencies of HLA-B*51:01 in patients with phenobarbital- and phenytoin-induced SJS/TEN and in controls were 75.0, 55.6 and 15.2%, respectively. HLA-A*02:07 and HLA-B*51:01, in a dominant model, were significantly associated with zonisamide- and phenobarbital-induced SJS/TEN, respectively (Pc = 0.0176 and 0.0042, respectively). CONCLUSION Our data suggest that HLA-A*02:07 and HLA-B*51:01 are potential biomarkers for zonisamide- and phenobarbital-induced SJS/TEN, respectively, in Japanese individuals.

Influence of CYP2C19 polymorphism and concomitant antiepileptic drugs on serum clobazam and N-desmethyl clobazam concentrations in patients with epilepsy.

Objective: The aims of this study were to identify the factors influencing the metabolism of clobazam (CLB) and its active metabolite [N-desmethyl clobazam (NCLB)] and to evaluate the NCLB concentration as an indicator for CYP2C19 polymorphism in epileptic patients. Methods: A total of 302 serum samples from 238 Japanese patients were evaluated. The ratios of the serum CLB and NCLB concentrations to the CLB dose (CD ratios) were calculated and compared with CYP2C19 phenotypes. Results: The mean CD ratio of NCLB in extensive metabolizers (EM: *1/*1), intermediate metabolizers (IM: *1/*2 or *1/*3), and poor metabolizers (PM: *2/*2, *3/*3, or *2/*3) was 3.1, 4.9, and 21.6 (&mgr;g/mL)/(mg/kg), respectively. In the EM and IM groups, the concomitant use of hepatic enzyme inducers (phenytoin and carbamazepine) reduced the CD ratio of CLB and increased that of NCLB. In the PM group, these inducers also decreased the CD ratio for CLB but did not elevate the CD ratio for NCLB. Using multiple regression analysis, body weight showed a positive correlation with an increased CD ratio for NCLB. The concomitant use of zonisamide and stiripentol also elevated the CD ratio for NCLB in the EM and IM groups, but that of the PM group was almost unchanged. When the cut-off value of the CD ratio for NCLB was set as 10.0 (&mgr;g/mL)/(mg/kg) for predicting the CYP2C19 PM status, the sensitivity and specificity were 94.4% and 95.7%, respectively. Conclusions: The interaction between NCLB and other antiepileptic drugs showed marked differences among CYP2C19 phenotypes. Measurement of the serum NCLB concentration is clinically useful for identifying the PM phenotype.

A case of early onset epileptic encephalopathy with de novo mutation in SLC35A2: Clinical features and treatment for epilepsy

INTRODUCTION Mutations of SLC35A2 that encodes Golgi-localized Uridine diphosphate (UDP)-galactose transporter at Xp11.23 lead to congenital disorders of glycosylation (CDG). Although patients with CDG generally have diverse systemic symptoms, patients with a SLC35A2 mutation manifest predominantly disorders of the central nervous system (CNS). CASE REPORT A female infant aged 12months was referred to our center because of intractable seizures. The patient was born with birth weight of 3228g after 40weeks of unremarkable gestation. At the age of 2months, she had partial seizures evolving to epileptic spasms. Her electroencephalogram showed hypsarrhythmia. Her seizures were refractory to antiepileptic drugs. At referral to our center at 12months, she had developmental delay (no head control), widely spaced inverted nipples, external strabismus, and bilateral heterochromia of irises. Blood examinations were normal. Brain magnetic resonance imaging findings included cerebral and cerebellar atrophy, thinning of the corpus callosum, and arachnoid pouch. Whole-exome sequencing detected a de novo frameshift mutation c.950delG (p.Gly317Alafs*32) at exon 4 in SLC35A2. Seizures subsided after the second adrenocorticotropic hormones (ACTH) therapy at 18months. At the age of 36months, although she had intellectual disability with no meaningful words, she was seizure-free and was able to sit without support and showed smiling face a lot. CONCLUSION This report reviewed the clinical features of patients with a SLC35A2 mutation. ACTH therapy may be effective for refractory epilepsy in these patients.

Developmental outcome after surgery in focal cortical dysplasia patients with early-onset epilepsy

The purpose of this study was to investigate the developmental outcome after surgery for early-onset epilepsy in patients with focal cortical dysplasia (FCD). Among 108 patients with histopathologically confirmed FCD operated between 1985 and 2008, we selected 17 patients with epilepsy onset up to 3 years of age. Development was evaluated by the developmental quotient or intelligence quotient (DQ-IQ) and mental age was measured by the Mother-Child Counseling baby test or the Tanaka-Binet scale of intelligence. Postsurgical development outcome was evaluated by the changes in DQ-IQ and mental age as well as rate of increase in mental age (RIMA) after surgery. RIMA was calculated as the increase in mental age per chronological year (months/year; normal average rate: 12 months/year). Age at epilepsy onset of 17 patients ranged from 15 days to 36 months (mean±SD, 11.0±10.0 months). Age at surgery ranged from 18 to 145 months (75.1±32.4 months). Evaluation just before surgery showed that 13 of 17 (76.4%) patients had DQ-IQ below 70. Ten patients (58.8%) were seizure-free throughout the postsurgical follow-up period. After surgery, DQ-IQ was maintained within 10 points of the presurgical level in 13 patients (76.4%), and increased by more than 10 points in one patient (5.9%). After surgery, RIMA in patients with Engels class I (7.5±3.8) was higher than patients with Engels class II-IV (2.6±3.4) (unpaired t-test with Welchs correction, t=2.99, df=15, p=0.0092). RIMA was particularly low in two patients with spasm. In four patients with presurgical DQ-IQ<70, seizure-free after surgery and without spasm, DQ-IQ did not increase but RIMA improved from 3.6±2.8 before surgery to 6.9±2.5 months/year after surgery. RIMA became better from 2 years after surgery. In four patients with presurgical DQ-IQ≥70 and no spasm, two showed the same or higher RIMA than normal average after surgery. In 58.8% of FCD patients with early onset epilepsy, epilepsy surgery effectively controlled seizures, and in 82.3% of patients, epilepsy surgery preserved or improved development. Residual seizures after surgery and lower DQ-IQ before surgery might be potential risk factors for poor development after surgery. In patients of Engels class I with lower presurgical DQ-IQ, catch-up increase in mental age was observed after two years following surgery.