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Mutations in Lysine-Specific Histone Methyltransferase 2B gene (KMT2B) have been reported to be associated with isolated and complex early-onset generalized dystonia. We describe clinico-genetic features on a Greek patient with a novel de novo variant and demonstrate the phenotypic spectrum of KMT2B variants. We performed whole exome sequencing (WES), in a Greek patient with sporadic generalized dystonia. Additionally, we performed a systematic review of all published cases with KMT2B variants. The patient presented with isolated and mild generalized dystonia. We identified a novel splice site variant that was confirmed by Sanger sequencing and was not found in parents. This is the first reported KMT2B variant, in the Greek population. This case report further highlights the growing trend of identifying genetic diseases previously restricted to few cases in many different ethnic groups worldwide via exome sequencing. In the systematic review, we evaluated the mutation pathogenicity in all previously reported cases to investigate possible phenotype-genotype correlations. Greater mutation numbers in different populations will be important and mutation-specific functional studies will be essential to identify the pathogenicity of the various KMT2B variants.

Mutations in the gene encoding amyloid precursor protein (APP) cause autosomal dominant inherited Alzheimer’s disease (AD). We present a case of a 68-year-old female who presented with epileptic seizures, neuropsychiatric symptoms and progressive memory decline and was found to carry a novel APP variant, c.2062T>G pLeu688Val. A comprehensive literature review of all reported cases of AD due to APP mutations was performed in PubMed and Web of Science databases. We reviewed 98 studies with a total of 385 cases. The mean age of disease onset was 51.3 ± 8.3 (31–80 years). Mutations were most often located in exons 17 (80.8%) and 16 (12.2%). The most common symptoms were dementia, visuospatial symptoms, aphasia, epilepsy and psychiatric symptoms. Mutations in the β-amyloid region, and specifically exon 17, were associated with high pathogenicity and a younger age of disease onset. We describe the second reported APP mutation in the Greek population. APP mutations may act variably on disease expression and their phenotype is heterogeneous.

ObjectiveThe aim of this study was to evaluate the correlation between the various NOTCH3 mutations and their clinical and genetic profile, along with the presentation of a novel mutation in a patient.MethodsHere, we describe the phenotype of a patient with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) harboring a novel mutation. We also performed an extensive literature research for NOTCH3 mutations published since the identification of the gene and performed a systematic review of all published cases with NOTCH3 mutations. We evaluated the mutation pathogenicity in a great number of patients with detailed clinical and genetic evaluation and investigated the possible phenotype-genotype correlations.ResultsOur patient harbored a novel mutation in the NOTCH3 gene, the c.3084 G > C, corresponding to the aminoacidic substitution p.Trp1028Cys, presenting with seizures as the first neurologic manifestation. We managed to find a correlation between the pathogenicity of mutations, severity of the phenotype, and age at onset of CADASIL. Significant differences were also identified between men and women regarding the phenotype severity.ConclusionsThe collection and analysis of these scarce data published since the identification of NOTCH3 qualitatively by means of a systematic review and quantitatively regarding genetic profile and pathogenicity scores, highlight the significance of the ongoing trend of investigating phenotypic genotypic correlations.