Perinatal and neonatal characteristics of Prader-Willi syndrome in Japan.

BACKGROUND: Prader-Willi syndrome (PWS) is suspected at birth if extreme hypotonia, difficulty in feeding, hypogonadism, and failure to thrive are present. Genetic diagnosis of PWS can generally be made within the first few months of life; however, a delayed diagnosis of PWS is frequently reported. Although the clinical characteristics of perinatal and neonatal patients with PWS have been reported, there are no such reports on the clinical characteristics of these patients in Japan. METHODS: This retrospective, single-center study involved 177 Japanese patients with PWS and their medical data regarding the perinatal and neonatal periods were evaluated. RESULTS: The median maternal age at birth was 34 years; 12.7% of the mothers had a history of assisted reproductive technology (ART). Of the mothers, 13.5% reported polyhydramnios and 4.3% had oligohydramnios. Decreased fetal movement during pregnancy was reported by 76% of the mothers. A total of 60.5% of patients were born by cesarean section. Genetic subtypes included deletions (66.1%), uniparental disomy (31.0%), imprinting defects (0.6%), and other or unknown subtypes (2.3%). The median birth length was 47.5 cm and the median birthweight was 2476 g. Of the 160 patients, 14 (8.8%) were classified as small for gestational age. Most patients had hypotonia (98.8%), and 89.3% required gavage feeding at birth. Breathing problems, congenital heart disease, and undescended testis were noted in 33.1%, 7.0%, and 93.5% of patients, respectively. CONCLUSION: In our study, higher rates of ART, polyhydramnios, decreased fetal movements, cesarean section, hypotonia, feeding difficulties, and undescended testis were observed in PWS.

Effects of growth hormone treatment on thyroid function in pediatric patients with Prader-Willi syndrome.

It is unclear whether hypothyroidism is present in patients with Prader-Willi syndrome (PWS). This study aimed to clarify the state of the hypothalamic-pituitary-thyroid axis and the effects of growth hormone (GH) treatment on thyroid function in pediatric patients with PWS. We retrospectively evaluated thyroid function in 51 patients with PWS before GH treatment using a thyroid-releasing hormone (TRH) stimulation test (29 males and 22 females; median age, 22 months). We also evaluated the effect of GH therapy on thyroid function by comparing serum free triiodothyronine (fT3), free thyroxine (fT4), and thyroid stimulating hormone (TSH) levels at baseline, 1 year, and 2 years after GH therapy. TSH, fT4, and fT3 levels were 2.28 µU/ml (interquartile range [IQR]; 1.19-3.61), 1.18 ng/dl (IQR; 1.02-1.24), and 4.02 pg/dl (IQR; 3.54-4.40) at baseline, respectively. In 49 of 51 patients, the TSH response to TRH administration showed a physiologically normal pattern; in two patients (4.0%), the pattern suggested hypothalamic hypothyroidism (delayed and prolonged TSH peak after TRH administration). TSH, fT4, and fT3 levels did not change significantly during 1 or 2 years after GH treatment. The TSH response to TRH showed a normal pattern in most patients, and thyroid function did not change significantly during the 2 years after initiating GH treatment.

Delayed peak response of cortisol to insulin tolerance test in patients with Prader-Willi syndrome.

Deaths among children with Prader-Willi syndrome (PWS) are often related to only mild or moderate upper respiratory tract infections, and many causes of death remain unexplained. Several reports have hypothesized that patients with PWS may experience latent central adrenal insufficiency. However, whether PWS subjects suffer from alteration of the hypothalamus-pituitary-adrenal (HPA) axis remains unclear. This study aimed to explore the HPA axis on PWS. We evaluated the HPA axis in 36 PWS patients (24 males, 12 females; age range, 7 months to 12 years; median age 2.0 years; interquartile range [IQR], 1.5-3.4 years) using an insulin tolerance test (ITT) in the morning between 08:00 and 11:00. For comparison, ITT results in 37 age-matched healthy children evaluated for short stature were used as controls. In PWS patients, basal levels of adrenocorticotropic hormone (ACTH) were 13.5 pg/ml (IQR, 8.3-27.5 pg/ml) and basal levels of cortisol were 18.0 µg/dl (IQR, 14.2-23.7 µg/dl). For all patients, cortisol levels at 60 min after stimulation were within the reference range (>18.1 µg/dl), with a median peak of 41.5 µg/dl (IQR, 32.3-48.6 µg/dl). Among control children, basal level of ACTH and basal and peak levels of cortisol were 10.9 (IQR, 8.5-22.0 pg/ml), 15.6 (IQR, 11.9-21.6 µg/dl), and 27.8 µg/dl (IQR, 23.7-30.5 µg/dl), respectively. Basal and peak levels of cortisol were all within normal ranges, but peak response of cortisol to ITT was delayed in the majority of PWS patients (64%). Although the mechanism remains unclear, this delay may signify the existence of central obstacle in adjustment of the HPA axis.

Decline of CSF orexin (hypocretin) levels in Prader-Willi syndrome.

Prader-Willi syndrome is a congenital neurodevelopmental disorder resulting from deletion of the paternal copies of genes within the chromosome region 15q11-q13. Patients with Prader-Willi syndrome often exhibit excessive daytime sleepiness, excessive appetite, and obesity. As is the case in narcolepsy, orexin (hypocretin) may be responsible for these symptoms. However, reports showing cerebrospinal fluid orexin levels in Prader-Willi syndrome patients have been limited. The aim of this study was to examine the relationship between the characteristic symptoms of Prader-Willi syndrome and cerebrospinal fluid orexin levels. We clinically identified 14 Prader-Willi syndrome patients and examined their cerebrospinal fluid orexin levels. A total of 12 patients with a 15q11-q13 deletion and two patients with maternal uniparental disomy of chromosome 15 were identified. A total of 37 narcoleptic patients and 14 idiopathic hypersomnia patients were recruited for comparison. Cerebrospinal fluid orexin levels (median [25-75 percentiles]) in the 14 Prader-Willi syndrome patients were intermediate (192 [161-234.5] pg/ml), higher than in the narcoleptic patients, but lower than in the idiopathic hypersomnia patients. Body mass index of the Prader-Willi syndrome patients was higher than in the narcoleptic and idiopathic hypersomnia patients. There was also a negative correlation between Epworth sleepiness scale scores and orexin levels in Prader-Willi syndrome patients. Decreased cerebrospinal fluid orexin levels in Prader-Willi syndrome may play an important role in severity of obesity and excessive daytime sleepiness.

Growth references for Japanese individuals with Noonan syndrome.

BACKGROUND: Noonan syndrome (NS) is a clinically and genetically heterogeneous syndrome characterized by distinctive facial features, short stature, congenital heart diseases, and other comorbidities. NS-specific growth charts are essential for NS care, but currently no such charts are available for Asian populations. METHODS: We conducted a nationwide survey by collaborating with three academic societies in Japan. We obtained the data of 356 clinically diagnosed NS subjects from 20 hospitals. The Lambda-Mu-Sigma method was used for establishing growth charts. RESULTS: A total of 308 subjects (males: 159 and females: 149) were analyzed after excluding 48 subjects because of missing auxological data (26 subjects), presence of complications affecting growth (5 subjects), and extreme longitudinal growth aberrations which lay more than three standard deviation scores from the mean in this population (17 subjects). Genetic analyses were performed in 150 patients (48.7%); 103 (68.7%) were reported to have some abnormalities in the known causative genes. Cardiovascular diseases were found in 256 patients (83.1%). The NS-specific height, weight, and BMI charts were constructed with 3,249 mixed longitudinal and cross-sectional measurements. CONCLUSION: Growth standards for Japanese individuals with NS were established. These charts are expected to be used in various clinical settings.

Effects of financial support on treatment of adolescents with growth hormone deficiency: a retrospective study in Japan.

BACKGROUND: Treatment costs for children with growth hormone (GH) deficiency are subsidized by the government in Japan if the children meet clinical criteria, including height limits (boys: 156.4 cm; girls: 145.4 cm). However, several funding programs, such as a subsidy provided by local governments, can be used by those who exceed the height limits. In this study, we explored the impacts of financial support on GH treatment using this natural allocation. METHODS: A retrospective analysis of 696 adolescent patients (451 boys and 245 girls) who reached the height limits was conducted. Associations between financial support and continuing treatment were assessed using multiple logistic regression analyses adjusting for age, sex, height, growth velocity, bone age, and adverse effects. RESULTS: Of the 696 children in the analysis, 108 (15.5 %) were still eligible for financial support. The proportion of children who continued GH treatment was higher among those who were eligible for support than among those who were not (75.9 % vs. 52.0 %, P < 0.001). The odds ratios of financial support to continuing treatment were 4.04 (95 % confidence interval [CI]: 1.86-8.78) in boys and 1.72 (95 % CI: 0.80-3.70) in girls, after adjusting for demographic characteristics and clinical factors. CONCLUSIONS: Financial support affected decisions on treatment continuation for children with GH deficiency. Geographic variations in eligibility for financial support pose an ethical problem that needs policy attention. An appropriate balance between public spending on continuation of therapy and improved quality of life derived from it should be explored.

Comparative analysis of autistic traits and behavioral disorders in Prader-Willi syndrome and Asperger disorder.

Prader-Willi syndrome (PWS) is a neuro-genetic disorder caused by the absence/loss of expression of one or more paternally expressed genes on chromosome 15 (q11-13). In this study, a comparative analysis of intelligence level and autistic traits was conducted between children with PWS (n = 30; 18 males, 12 females; age = 10.6 ± 2.8 years) and those with Asperger disorder (AD; n = 31; 24 males, 7 females; age = 10.5 ± 3.1 years). The children were compared by age group: lower elementary school age (6-8 years), upper elementary school age (9-12 years), and middle school age (13-15 years). As results, the intelligence levels of children with PWS were significantly lower than those with AD across all age groups. Autistic traits, assessed using the Pervasive Developmental Disorders Autism Society Japan Rating Scale (PARS), revealed that among elementary school age children, those with PWS had less prominent autistic traits than those with AD, however, among middle school age children, those with PWS and AD showed similar prominence. An analysis of the PARS subscale scores by age group showed that while the profiles of autistic traits for children with PWS differed from those of children with AD at elementary school age, the profiles showed no significant differences between the groups at middle school age. The findings suggest that autistic traits in PWS become gradually more prominent with increasing of age and that these autistic traits differ in their fundamental nature from those observed in AD.

Selection of infants who potentially have congenital anomalies of the kidney and urinary tract from a large cohort for a more thorough examination.

BACKGROUND: Although congenital anomalies of the kidney and urinary tract (CAKUT) are the most common cause of pediatric end-stage renal disease (ESRD), little is known about the characteristics exhibited in the infantile period by CAKUT patients who develop ESRD. Further, an efficient screening method for CAKUT diagnosis is not available currently. In the present study, we aimed to develop a method to select infants who potentially have CAKUT from a large group of infants. METHODS: We retrospectively investigated the clinical characteristics of CAKUT patients in the infantile period. The medical records of 101 patients with CAKUT who had undergone dialysis or renal transplantation were reviewed. The data of gestational age, birth weight, oligohydramnios, poor body weight gain, asphyxia, and jaundice were recorded. We attempted to determine the ideal characteristics that could be used to select infants who potentially have CAKUT. RESULTS: 14 % of patients were born prematurely, 18 % had low birth weight, 79 % had poor body weight gain, 18 % had asphyxia, 8 % had oligohydramnios, and 12 % had jaundice. We found that 82 % of patients had poor body weight gain or oligohydramnios among our patients and regarded these two symptoms as ideal markers for selecting those who potentially have CAKUT (specificity, 95 %; efficacy, 95 %). Further, the age of ≤ 7 months was the most appropriate time for the selection. CONCLUSIONS: For timely diagnosis of CAKUT, we recommend that ultrasound examination and the serum creatinine test be conducted for infants showing poor body weight gain or oligohydramnios at age ≤ 7 months.

The characteristics of scoliosis in Prader-Willi syndrome (PWS): analysis of 58 scoliosis patients with PWS.

BACKGROUND: The purpose of this study was to compare the characteristics of scoliosis in Prader-Willi syndrome (PWS) patients versus idiopathic scoliosis (IS). METHODS: We identified 193 PWS patients. Scoliosis was found in 58 PWS patients, 39 of whom were treated with GH. Fifty-five IS patients were consecutively selected from an outpatient clinic. We investigated 113 patients (58 PWS group, 55 IS group) followed for a minimum of 2 years. The mean age was 17.9 and 16.1 years, respectively. Deformity was measured using Lenke classification, Cobb angle, thoracic kyphosis at T2-5 and T5-12, lumbar lordosis at T12-S1, and sagittal alignment at the C7 plumb line. BMI was also recorded. RESULTS: According to the Lenke system, patients were classified as (PWS group/IS group): Type 1 (8/26), Type 2 (1/4), Type 3 (3/15), Type 4 (1/0), Type 5 (32/8), and Type 6 (13/2). The average Cobb angles were 32.6° in the PWS and 35.4° in the IS. No significant differences were found for the thoracic kyphosis (T2-5, T5-12), lumbar lordosis (T12-S1) or C7 plumb line between the two groups. BMI was increased in the PWS group not treated previously with GH as compared with the IS group and the PWS group with GH. CONCLUSIONS: Most PWS patients presented with lumbar or thoracolumbar curves (Type 5, 6), whereas IS patients typically had thoracic scoliosis (Type 1, 2, 3).

Improved liver function and relieved pruritus after 4-phenylbutyrate therapy in a patient with progressive familial intrahepatic cholestasis type 2.

To examine the effects of 4-phenylbutyrate (4PB) therapy in a patient with progressive familial intrahepatic cholestasis type 2. A homozygous c.3692G>A (p.R1231Q) mutation was identified in ABCB11. In vitro studies showed that this mutation decreased the cell-surface expression of bile salt export pump (BSEP), but not its transport activity, and that 4PB treatment partially restored the decreased expression of BSEP. Therapy with 4PB had no beneficial effect for 1 month at 200 mg/kg/day and the next month at 350 mg/kg/day but partially restored BSEP expression at the canalicular membrane and significantly improved liver tests and pruritus at a dosage of 500 mg/kg/day. We conclude that 4PB therapy would have a therapeutic effect in patients with progressive familial intrahepatic cholestasis type 2 who retain transport activity of BSEP per se.

Mutation spectrum and phenotypic variation in nine patients with SOX2 abnormalities.

Multiple mutations in SOX2 have been identified in patients with ocular anomalies and/or pituitary dysfunction. Here, we identified SOX2 abnormalities in nine patients. The molecular defects included one missense, one nonsense and four frameshift mutations, and three submicroscopic deletions involving SOX2. Three of the six mutations and all deletions were hitherto unreported. The breakpoints determined in one deletion were located within Alu repeats and accompanied by an overlap of 11 bp. Three of the six mutations encoded SOX2 proteins that lacked in vitro transactivation activity for the HESX1 promoter, whereas the remaining three generated proteins with ∼15-∼20% of transactivation activity. All cases manifested ocular anomalies of various severities, together with several complications including arachnoid cyst and hamartoma. There was no apparent correlation between the residual activity and clinical severity. The results indicate that molecular defects in SOX2 are highly variable and include Alu repeat-mediated genomic rearrangements. Our data provide further evidence for wide phenotypic variation of SOX2 abnormalities and the lack of genotype-phenotype correlation in patients carrying SOX2 lesions.

Autism spectrum disorders and hyperactive/impulsive behaviors in Japanese patients with Prader-Willi syndrome: a comparison between maternal uniparental disomy and deletion cases.

This study aims to compare maternal uniparental disomy 15 (mUPD) and a paternal deletion of 15q11-13 (DEL) of Prader-Willi syndrome (PWS) in regard to autism spectrum disorders (ASD). Forty-five Japanese individuals with PWS were recruited from a single recruitment center. The participants consisted of 22 children (aged from 6 to 12) and 23 adolescents (aged from 13 to 19). Six children and seven adolescents were confirmed as having mUPD. Sixteen children and 16 adolescents were confirmed as having DEL. Under blindness to the participants' genotypes, a single psychologist carried out behavioral and psychological assessments, including the Wechsler Intelligence Scales, Pervasive Developmental Disorders Autism Society Japan Rating Scale (PARS), and ADHD-Rating Scale-IV (ADHD-RS-IV). Two comparisons were made: one between mUPD and DEL children and another between mUPD and DEL adolescents. In children, no significant differences were found between mUPD and DEL participants in terms of autistic (PARS childhood, P = 0.657) and impulsive behaviors (ADHD-RS-IV hyperactive/impulsive, P = 0.275). In adolescents, mUPD patients showed significantly more autistic symptomatology (PARS adolescent, P = 0.027) and significantly more impulsive behavior (ADHD-RS-IV hyperactive/impulsive, P = 0.01) than DEL patients. Our findings about Japanese PWS patients were consistent with previous researches from western countries not focused on Asian patients, indicating that mUPD cases would be more prone to ASD than DEL cases, regardless of ethnoregional differences. In addition, our data suggested that the behavioral difference between mUPD and DEL cases in terms of autistic and impulsive symptoms tend to be unrecognizable in their childhood.

QOL in caregivers of Japanese patients with Prader-Willi syndrome with reference to age and genotype.

This study aimed to measure quality of life (QOL) of the primary family caregivers for patients with Prader-Willi syndrome (PWS). Comparisons were made between caregivers' QOL in regard to their dependents' genotype and age group. The participants with PWS consisted of 22 children (aged from 6 to 12 years) and 23 adolescents (aged from 13 to 19 years), including 6 children and 7 adolescents with maternal uniparental disomy (mUPD) and 16 children and 16 adolescents with deletion (DEL). The QOL of the primary family caregiver for each patient was assessed using the Japanese version of the WHOQOL-BREF. To examine the effect that age (children vs. adolescents) and genotype (DEL vs. mUPD) have on the QOL of caregivers, a two-way ANOVA was conducted, followed by the Bonferroni procedure to test the simple main effects. The two age groups and the two genotypes of PWS were used as independent variables and the total QOL of caregivers as a dependent variable. The two-way ANOVA (F(1, 41) = 6.98, P < 0.05), followed by the Bonferroni procedure, showed the following: the total QOL of caregivers of DEL adolescents showed little difference from that with DEL children, but the QOL of caregivers for mUPD adolescents was shown to be lower than that with mUPD children along with that of caregivers with DEL adolescents. There is hence a growing tendency for the deterioration in the QOL of caregivers to manifest itself later in the patients' adolescence, found mainly with mUPD patients.

Exacerbation of BMI after cessation of growth hormone therapy in patients with Prader-Willi syndrome.

Long-term treatment with growth hormone (GH) in patients with Prader-Willi syndrome (PWS) improves not only height velocity, height standard deviation score, and final height, but also the degree of obesity and body composition abnormalities. Anecdotally, PWS patients tend to suffer from severe obesity and its complications after cessation of GH therapy. However, there have been no studies to investigate changes in body mass index (BMI) and adipose tissue distribution after cessation of GH therapy in young PWS patients. Therefore, we investigated changes in the BMI-standard deviation score (SDS) and adipose tissue distribution after cessation of GH therapy in PWS patients. We evaluated 14 PWS patients. BMI-SDS was calculated at 0, 6, 12, 18, and 24 months before and after cessation of GH treatment. We also evaluated subcutaneous adipose tissue (SAT) (cm(2)) and visceral adipose tissue (VAT) (cm(2)) area in 8 of the 14 study patients with single slice abdominal computed tomography at the level of the umbilicus. The BMI-SDS significantly increased at 6, 12, 18, and 24 months after cessation of GH therapy (P = 0.039, P = 0.008, P = 0.003, P = 0.003, respectively). There was a tendency toward increases in VAT at 12 and 24 months after cessation of GH therapy, but the increases did not reach statistical significance (P = 0.062, P = 0.125, respectively). Therefore, cessation of GH therapy in PWS patients worsened BMI. To maintain good body composition and prevent complications of obesity, long-term use of GH in adult PWS patients may be advisable.

Compound heterozygous deletions in pseudoautosomal region 1 in an infant with mild manifestations of langer mesomelic dysplasia.

Haploinsufficiency of SHOX on the short arm pseudoautosomal region (PAR1) leads to Leri-Weill dyschondrosteosis (LWD), and nullizygosity of SHOX results in Langer mesomelic dysplasia (LMD). Molecular defects of LWD/LMD include various microdeletions in PAR1 that involve exons and/or the putative upstream or downstream enhancer regions of SHOX, as well as several intragenic mutations. Here, we report on a Japanese male infant with mild manifestations of LMD and hitherto unreported microdeletions in PAR1. Clinical analysis revealed mesomelic short stature with various radiological findings indicative of LMD. Molecular analyses identified compound heterozygous deletions, that is, a maternally inherited ∼46 kb deletion involving the upstream region and exons 1-5 of SHOX, and a paternally inherited ∼500 kb deletion started from a position ∼300 kb downstream from SHOX. In silico analysis revealed that the downstream deletion did not affect the known putative enhancer regions of SHOX, although it encompassed several non-coding elements which were well conserved among various species with SHOX orthologs. These results provide the possibility of the presence of a novel enhancer for SHOX in the genomic region ∼300 to ∼800 kb downstream of the start codon.

Epilepsy and West syndrome in neonates with hypoxic-ischemic encephalopathy.

BACKGROUND: Perinatal hypoxic-ischemic encephalopathy (HIE) has been linked to the development of late-onset seizures. The aim of the present study was to determine the incidence of epilepsy and West syndrome in children with perinatal HIE and identify factors associated with the development of postnatal seizure disorders. METHODS: We retrospectively enrolled 208 term and late-preterm infants diagnosed with perinatal HIE from April 2000 to March 2009 at Saitama Children's Medical Center. Children with obvious multiple anomalies and known chromosomal abnormalities were excluded. A questionnaire was distributed to parents to determine seizure-related outcomes. Medical records were retrospectively reviewed and relevant clinical parameters were analyzed. RESULTS: In total, 162 questionnaires were answered (77.9%). Of the 162 subjects, 26 (16.0%) developed epilepsy, and eight subjects (4.9%) were diagnosed with West syndrome. Neonatal seizures occurred in 72 subjects (44.4%). The incidence of epilepsy and West syndrome was significantly higher in infants who experienced neonatal seizures than in those without seizure history. A total of 82 subjects were diagnosed with moderate (n = 52) or severe HIE (n = 30), of whom 57 subjects (69.5%) received therapeutic hypothermia. The incidence of epilepsy was significantly lower in these treated subjects. In addition, subjects with moderate or severe HIE were significantly more likely to develop late-onset epilepsy and West syndrome than those with mild HIE. CONCLUSIONS: The severity of perinatal HIE and neonatal seizures is a potential risk factor for the development of late-onset seizures. Therapeutic hypothermia may reduce the risk of the development of epilepsy in such cases.

Growth hormone treatment for osteoporosis in patients with scoliosis of Prader-Willi syndrome.

BACKGROUND: Patients with Prader-Willi syndrome (PWS) have fragile bones. Osteoporosis is a major concern in scoliosis surgery. Our aim was to investigate bone mineral density (BMD) in PWS patients and to verify the efficacy of and scoliosis deterioration with growth hormone (GH) administration for osteoporosis. METHODS: We followed 148 PWS patients who underwent lumbar spine (L2-4) BMD testing. Sixty-four patients had scoliosis, and 84 were non-scoliosis patients. Patients were treated with GH (0.245 mg/kg/week) until they reached a skeletal age of 17 years for males and 15 years for females. We also evaluated the effect of GH treatment on BMD in 101 patients (60 males, 41 females) undergoing BMD testing more than twice. The mean patient age was 5.4 years. The mean duration of GH administration was 54 months. RESULTS: Mean lumbar BMD was 0.567 g/cm(2). Fifty patients (33.8%) had osteoporosis and 41 (27.7%) had osteopenia. There was no significant difference in mean BMD between patients with scoliosis (0.598 g/cm(2)) and without scoliosis (0.548 g/cm(2)). GH treatment caused a significant increase in Z score (pre-GH: mean -2.28 vs. post-GH: mean -1.53, P < 0.001). There was no statistical difference in the prevalence of scoliosis between the GH treatment group (45/112, 40.1%) and non-treatment group (19/36, 52.8%). CONCLUSIONS: Among patients with PWS, 61.5% had low BMDs. GH administration significantly improved the lumbar BMD (Z score). There were no statistically significant differences in the prevalence of scoliosis among patients who received GH treatment compared to patients who did not.

Dominant-negative mutations in alpha-II spectrin cause West syndrome with severe cerebral hypomyelination, spastic quadriplegia, and developmental delay.

A de novo 9q33.3-q34.11 microdeletion involving STXBP1 has been found in one of four individuals (group A) with early-onset West syndrome, severe hypomyelination, poor visual attention, and developmental delay. Although haploinsufficiency of STXBP1 was involved in early infantile epileptic encephalopathy in a previous different cohort study (group B), no mutations of STXBP1 were found in two of the remaining three subjects of group A (one was unavailable). We assumed that another gene within the deletion might contribute to the phenotype of group A. SPTAN1 encoding alpha-II spectrin, which is essential for proper myelination in zebrafish, turned out to be deleted. In two subjects, an in-frame 3 bp deletion and a 6 bp duplication in SPTAN1 were found at the initial nucleation site of the alpha/beta spectrin heterodimer. SPTAN1 was further screened in six unrelated individuals with WS and hypomyelination, but no mutations were found. Recombinant mutant (mut) and wild-type (WT) alpha-II spectrin could assemble heterodimers with beta-II spectrin, but alpha-II (mut)/beta-II spectrin heterodimers were thermolabile compared with the alpha-II (WT)/beta-II heterodimers. Transient expression in mouse cortical neurons revealed aggregation of alpha-II (mut)/beta-II and alpha-II (mut)/beta-III spectrin heterodimers, which was also observed in lymphoblastoid cells from two subjects with in-frame mutations. Clustering of ankyrinG and voltage-gated sodium channels at axon initial segment (AIS) was disturbed in relation to the aggregates, together with an elevated action potential threshold. These findings suggest that pathological aggregation of alpha/beta spectrin heterodimers and abnormal AIS integrity resulting from SPTAN1 mutations were involved in pathogenesis of infantile epilepsy.

Evaluating the frequency and characteristics of seizures in 142 Japanese patients with Prader-Willi syndrome.

Prader-Willi syndrome (PWS) has not been widely regarded as a disorder with a risk factor for seizures. We retrospectively investigated the frequency and characteristics of seizures and examined genotype-phenotype correlations with respect to seizures in PWS. We analyzed 142 patients with PWS and identified 31 (22%) with seizures. The most common seizure type was febrile convulsion (12%, 17/142). Epilepsy occurred in 6% of the patients in our cohort (9/142). The frequencies of febrile seizure and epilepsy in PWS were higher than those in the general population. Our study suggested that the frequency of seizures was not associated with genotypes of PWS (P = 0.35). In our study patients with PWS, 68% of the patients with seizures experienced initial episodes before they were 2 years old, and the seizures were relatively easier to manage.