Genetic landscape of Rett syndrome-like phenotypes revealed by whole exome sequencing.

BACKGROUND: Rett syndrome (RTT) is a characteristic neurological disease presenting with regressive loss of neurodevelopmental milestones. Typical RTT is generally caused by abnormality of methyl-CpG binding protein 2 (MECP2). Our objective to investigate the genetic landscape of MECP2-negative typical/atypical RTT and RTT-like phenotypes using whole exome sequencing (WES). METHODS: We performed WES on 77 MECP2-negative patients either with typical RTT (n=11), atypical RTT (n=22) or RTT-like phenotypes (n=44) incompatible with the RTT criteria. RESULTS: Pathogenic or likely pathogenic single-nucleotide variants in 28 known genes were found in 39 of 77 (50.6%) patients. WES-based CNV analysis revealed pathogenic deletions involving six known genes (including MECP2) in 8 of 77 (10.4%) patients. Overall, diagnostic yield was 47 of 77 (61.0 %). Furthermore, strong candidate variants were found in four novel genes: a de novo variant in each of ATPase H+ transporting V0 subunit A1 (ATP6V0A1), ubiquitin-specific peptidase 8 (USP8) and microtubule-associated serine/threonine kinase 3 (MAST3), as well as biallelic variants in nuclear receptor corepressor 2 (NCOR2). CONCLUSIONS: Our study provides a new landscape including additional genetic variants contributing to RTT-like phenotypes, highlighting the importance of comprehensive genetic analysis.

[A case of long-term survival of a patient with infantile Alexander disease diagnosed by DNA analysis].

Alexander disease is a hereditary disorder of myelin degeneration. The pathological feature of the brain is the characteristic inclusion bodies in astrocytes called Rosenthal fibers. The major components of the Rosental fibers are known to be alpha B-crystallin and glial fibrillary acidic protein (GFAP). In recent years, reports have indicated mutations of the GFAP gene in patients with Alexander disease. The R239 mutation (R239C, R239H) tends to cause comparatively more severe conditions among the GFAP mutations. In this study. we examined a long-term survival case of a patient (age 25 years, 7 months) with infantile Alexander disease with an R239C mutation confirmed by DNA analysis. There are no past reports of subjects with the R239C mutation who had as prolonged a long-term survival as our case. Our subject's condition was not as severe as those with the R239H mutation. The clinical progress in those other reports also varied by case. The R239C mutation does not show as much correlation with the clinical presentation as the R239H mutation. We believe that factors such as the environment also play a part in the prognosis of the disease.

A case of megalencephalic leukoencephalopathy with subcortical cysts (van der Knaap disease): molecular genetic study.

Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is an autosomal recessive disorder characterized by macrocephaly, deterioration of motor function with ataxia, spasticity and mental decline. It has been revealed that the mutations in the gene, KIAA0027, were responsible for MLC and the gene was renamed subsequently 'MLC1'. A 41-year-old Japanese male with MLC, in whom a homozygous missense mutation, TCG to TTG at codon 93 resulting in S93L, was detected in the MLC1 gene, was described. MRI revealed marked cerebral atrophy and enlargement of the ventricular system. The subject's motor function had severely deteriorated, while his cognitive function had maintained at the level of a 2-year-old for the past 10 years. The mutation in the MLC1 gene of the patient is considered to be a common mutation responsible for MLC in Japanese patients because the same mutation had been detected in two other Japanese patients with MLC.

Molecular genetic study in Japanese patients with Alexander disease: a novel mutation, R79L.

Since the first report by Brenner et al. of mutations in the glial fibrillary acidic protein (GFAP) gene in patients with Alexander disease, several molecular genetic studies have been performed in different ethnic groups. We previously reported a Japanese patient with a mutation, R239C, which is identical to one commonly found in American patients. Here we have analyzed four additional Japanese patients by screening for known mutations or, if no known mutation was found, by sequencing of all exons of the GFAP gene. We detected three missense mutations; one was a novel mutation, R79L, and two were previously reported mutations, R239C and R79C. All of our patients were heterozygous for their mutations. Together with the novel mutation, R79L, four different nucleotide changes altering the R79 residue have been reported, implying that any alternation of this arginine residue can give the GFAP protein a dominant negative effect, leading to accumulation of GFAP as Rosenthal fibers. We conclude that molecular genetic analysis of the GFAP gene is feasible for antemortem diagnosis of Alexander disease in Japanese patients.

A case of X-linked agammaglobulinemia with progressive encephalitis.

This report describes a case of agammaglobulinemia with progressive encephalitis. The patient was a 6-year-old male who was diagnosed as having Bruton-type agammaglobulinemia at age 6 months. After the diagnosis was made, he received monthly intravenous immunoglobulin replacement with a residual immunoglobulin G level of more than 400 mg/dL. At 5 years of age, he presented with symptoms of mental deterioration and gait disturbance. He had no history of infection of the central nervous system. Brain biopsy revealed CD8-positive T-cell infiltration with cortical damage, but no infectious agents were observed by either immunohistochemistry or virus isolation. Treatment with subcutaneous interferon-alpha and high-dose intravenous immunoglobulin was begun, and clinical symptoms improved within a month. Hence, patients with agammaglobulinemia should be carefully monitored for complications of the central nervous system even if there is no history of infection.

[Serial median nerve SEPs and SSEPs in patients with West syndrome].

We studied serial median nerve somatosensory evoked potentials (SEPs) and short latency somatosensory evoked potentials (SSEPs) in 17 patients with West syndrome. Four of the 7 patients with absent SEPs in the initial examination showed recognizable SEPs in the follow-up studies, associated with improvement of electroencephalogram (EEG). This indicated that SEPs were variable with condition of epilepsy and lack of initial SEPs was not always a poor prognostic factor for seizure control and developmental outcome. Persistent lack of SEPs, however, indicated poor outcome of seizures, EEG and development. Central conduction time in SSEPs did not correlate with seizure or developmental outcome.

[Five patients with subacute sclerosing panencephalitis treated with intraventricular alpha-interferon and inosinpranobex].

We followed up 5 patients with subacute sclerosing panencephalitis (SSPE) for 14 to 81 months. They were treated with alpha-interferon (INF-alpha) and oral inosinpranobex (INP) in an early stage of Jabbour stage II and within 5 months after the onset. On admission, Ommaya reservoir was implanted for the intrathecal administration of INF-alpha. The dose was 1 x 10(5) U/m2 initially and daily increased to 1 x 10(6) U/m2. A total dose of 30 x 10(6) U/m3 was given to them over a 4-weeks to 6-weeks period. After discharge, a dose of 15 x 10(6) U/m2 in three patients was given weekly and a dose of 30 x 10(6) U/m2 in the other patients. In addition, all patients received oral INP. One patient showed mild progression and remained in early stage of Jabbour stage II. In the remaining 4 patients, the disease progressed to Jabbour stage III. Despite the small number of patients studied here, the results suggest that treatment with INF-alpha plus oral INP is ineffective in an early stage of SSPE.

[Epidemiology of subacute sclerosing panencephalitis in Okinawa, Japan--the second report 1977-1999].

There were 16 cases (11 males and 5 females) of SSPE in Okinawa from 1977 to 1999. The incidence was 0.58 per million population per year for the last 23 years, being higher than in other reports in Japan. Six of the 16 cases contracted measles in 1990. The measles antibody of SSPE cases after 1989 became lower than previously.

Autoantibodies and cell-mediated autoimmunity to NMDA-type GluRepsilon2 in patients with Rasmussen's encephalitis and chronic progressive epilepsia partialis continua.

PURPOSE: To evaluate antibody-mediated and cytotoxic T cell-mediated pathogenicity that has been implicated as the autoimmune pathophysiological mechanism in Rasmussen's encephalitis. METHODS: We examined autoantibodies against the N-methyl-d-aspartate glutamate receptor (NMDA-type GluR) epsilon2 subunit and its epitopes in serum and CSF samples from 20 patients [five histologically proven (definitive) Rasmussen's encephalitis with epilepsia partialis continua (EPC), four definitive Rasmussen's encephalitis without EPC, and 11 clinical Rasmussen's encephalitis with EPC]. We examined 3H-thymidine uptake into lymphocytes after stimulation by GluRs. RESULTS: All nine definitive patients (five patients with EPC and four without EPC), and 10 of 11 clinical Rasmussen's encephalitis patients had the autoantibodies. In four patients, the autoantibodies were absent in early stage when epileptic seizures had already become frequent, and appeared subsequently. In two patients, the autoantibodies persisted in the serum after frontal lobe resection or functional hemispherectomy, although epileptic seizures were completely controlled. Autoantibodies to the C2 epitope predominated, while autoantibodies to the extracellular N epitope were rare. The mean 3H-thymidine uptake ratios (stimulation by GluRepsilon2-containing homogenates/stimulation by PHA) were significantly higher in definitive and clinical Rasmussen encephalitis patients than in controls. The mean 3H-thymidine uptake ratios (relative to PHA) were significantly higher for GluRepsilon2-containing homogenate than for control homogenate or GluRdelta2-containing homogenate. CONCLUSIONS: Autoantibodies against GluRepsilon2 may be one of the diagnostic markers for Rasmussen's encephalitis with and without EPC. Patients have activated T cells stimulated by GluRepsilon2 in peripheral blood circulation. We speculate that cellular autoimmunity and the subsequent humoral autoimmunity against GluRepsilon2 may contribute to the pathophysiological processes in Rasmussen's encephalitis.