Mitochondrial disorders are considered to be the most common cause of metabolic abnormalities in the paediatric neurology population (Zeviani et al., 1996). These authors reported that the phenotypes observed in 25-30% of the paediatric patients in their neurology clinics were due to a mitochondrial aetiology. The genetic aetiology in an equivalently affected paediatric population in South Africa is currently unknown. This study investigated the possibility that reported mutations could account for the mitochondrial phenotypes observed in the South African population. It focussed on the most frequent paediatric mitochondrial disorders namely: Leigh Syndrome (LS), mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS), and myoclonic epilepsy and ragged red muscle fibres (MERRF). A clinically well characterised group of 25 patients with mitochondrial disorders was included in this study. The molecular analysis of the mitochondrial genome was initially based on a restriction fragment length polymorphism (RFLP) screening strategy for the ten most common mitochondrial DNA (mtDNA) mutations associated with the above¬mentioned three disorders. However, during the study the mutation analysis strategy was modified to a sequencing strategy as this provided more information than the RFLP approach. The modified sequencing strategy extended the study to incorporate fifteen additional mtDNA mutations, associated with other mitochondrial disorders, and individuals included in the study were thus investigated for the presence of 25 mtDNA mutations. Moreover, the modified strategy provided additional information of the regions encompassing the reported mutations. A single patient was observed to harbour the reported A3243G MELAS mutation. This mutation was noted to be heteroplasmic in the proband and two of her maternal relatives. None of the other 24 reported mutations were observed in this patient population. One novel mtDNA alteration in the tRNALeu(UUR) gene was observed in a single patient, although the pathogenicity of this mutation remains to be investigated. Novel and reported polymorph isms, some of which are associated with specific haplogroups, were also observed when comparing sequencing data against the Cambridge reference sequence. The data generated during this study contributed towards the understanding of the uniqueness of the South African population in the global context. This was apparent from the fact that only one of the reported mutations was observed in our patient population who were clinically well characterised and displayed phenotypes similar to those reported internationally. Results form this study underlined the complexity of mitochondrial disorders and argues in favour of whole mitochondrial genome sequence information to be used for diagnostic purposes. Moreover, the results confer with the hypothesis that novel mitochondrial mutations may account for the majority of mitochondrial phenotypes observed in the South African population. / Dissertation (MSc (Human Genetics))--University of Pretoria, 2007. / Genetics / unrestricted

Made available in DSpace on 2015-07-22T20:50:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-03-25 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Objetivos: avaliar a evolução clínica e eletrencefalográfica em 28 pacientes que tiveram diagnóstico de Síndrome de West (SW). Métodos: estudo retrospectivo no qual foram incluídos pacientes que tiveram diagnóstico clínico e eletrográfico de SW e admitidos para seguimento no Hospital São Paulo da Universidade Federal de São Paulo / Escola Paulista de Medicina, entre março de 2006 e dezembro de 2007. Todos foram submetidos a avaliações periódicas durante o tratamento da SW, incluindo VEEG e, no mínimo, um exame de VEEG, com duração de 6 a 12 horas, após o controle da SW por pelo menos um ano. Foram analisados dados demográficos, freqüência e semiologia das crises. Os EEGs e os VEEGs foram revisados para a quantificação e classificação das alterações eletrencefalográficas e das crises epilépticas. Resultados: a amostra foi composta por 28 pacientes com tempo médio de seguimento de 46,5 ± 13 meses, sendo 19 do sexo masculino (68%) e 9 (32%) do sexo feminino. A média de idade na admissão foi 10,5 ± 6,3 meses. Todos os pacientes apresentaram algum grau de atraso no DNPM. Os pacientes foram subdivididos em 2 grupos, criptogênicos (5 casos) e sintomáticos (23 casos). Dos 28 pacientes 16 (57%) evoluíram com crises epilépticas ao final do estudo e 12 (43%) evoluíram sem crises. Do total, 13 (46%) tiveram recidiva da SW. Dentre os 5 criptogênicos 4 (80%) evoluíram com controle de crises e dentre os 23 sintomáticos, apenas 8 (34,7%) evoluíram com controle das crises. Apenas 10,7% dos pacientes evoluíram para SLG (todos do grupo sintomático), permanecendo com crises de difícil controle até o final do seguimento. Dos que permaneceram com crises, 35,7% evoluíram para epilepsia focal, 14,2% com epilepsia generalizada e 7,1% tiveram ambos tipos de crises, focal e generalizada, sendo classificados como epilepsia indeterminada. Conclusões: A maioria dos casos de SW evoluiu para epilepsia focal, portanto, a SLG não foi a síndrome mais freqüente em nosso estudo. O grupo de pacientes sintomáticos apresentou pior evolução quanto ao controle das crises quando comparado com o grupo criptogênico. O tempo de duração da SW também influenciou na evolução. Recidiva da SW tem alta correlação com pior prognóstico. / Objectives: The goal of this study was to evaluate the clinical and electroencephalographic evolution of 28 patients that had WS. Patients and Methods: Retrospective study in which we included patients who had clinical diagnosis and electrographic of WS and admitted in the Hospital São Paulo, Federal University of São Paulo / Escola Paulista de Medicina, between March 2006 and December 2007, who had been submitted to periodic evaluations during treatment of SW, including video-EEG (VEEG) and, after controlling the same, at least, an examination of VEEG, lasting from 6 to 12 hours after the SW under control for at least 1 year. They were revised the handbooks of these patients for analysis of demographic data, frequency and semiology of seizures. The EEGs along the follow-up and the VEEGs were also reviewed for the quantification and classification of electroencephalographic changes and of epileptic seizures. Results: The sample consisted of 28 patients with mean follow-up of 46,5 ± 13 months, with 19 males (68%) and 9 (32%) female. The mean age at admission was 10,5 ± 6,3 months. All patients had some degree of delay in DNPM. The patients were divided into 2 groups, cryptogenics (5 cases) and symptomatics (23 cases). Of the 28 patients 16 (57%) evolved with seizures the end of the study and 12 (43%) evolved without crises. Of the total of patients, 13 (46%) had recurrence of the SW. Of the 5 cryptogenics 4 (80%) evolved with control of seizures and of the 23 symptomatic patients, only 8 (34,7%) evolved with control of the seizures. Only 10,7% of patients evolved to SLG (all of the symptomatic group) and remained with these crises difficult to control until the end of follow up. Of those who remain with crises, 35,7% evolved to focal epilepsy, 14,2% with generalized epilepsy and 7,1% had both types of crises, focal and generalized, being classified as undetermined epilepsy. Conclusions: The SLG wasn’t the evolution most frequent of the SW in our study. The most of these cases evolved with focal epilepsy. The group of symptomatic patients presented worse evolution in the control of seizures when compared with the group criptogenic. The time in which the patient remained in SW seems also influence the evolution. Recurrence of the SW has high correlation with poor prognosis. / TEDE / BV UNIFESP: Teses e dissertações