Relación entre el nivel de heteroplasmia de la mutación m.3243AG en diferentes tejidos y el fenotipo en familias con diabetes y sordera de herencia materna (midd) y melas

El MELAS y la Diabetes y Sordera de Herencia Materna (MIDD) son enfermedades mitocondriales producidas en la mayor parte de los casos por una misma mutación: la m.3243AG, la cual afecta al gen MT-TL1. Esto muestra la gran variabilidad fenotípica de dicha mutación. Una de las posibles causas de esta variación puede ser el nivel de heteroplasmia de la mutación. Este trabajo se propuso evaluar si existe relación entre el nivel de heteroplasmia en tres tejidos y el fenotipo. Fueron incluidas 3 familias con diagnóstico clínico de MELAS y 2 con diagnóstico clínico de MIDD. Se evaluó la presencia de la mutación y el nivel de heteroplasmia mediante ARMS-qPCR EN sangre, orina y mucosa oral. Una familia con MELAS resultó positiva para la mutación m.3243AG. Se evidenció una gran variabilidad fenotípica. El probando tenía una mayor heteroplasmia en los 3 tejidos en comparación con sus familiares oligosintomáticos. Se reporta el primer paciente en Colombia con MELAS y la mutación m.3271TC y se realizó un análisis de estas familiasAbstract. MELAS and Maternally Inherited Diabetes and Deafness (MIDD) are mitochondrial diseases produced in most cases by the same mutation: m.3243AG, which affects the MT-TL1 gene. This reveals the great phenotypic variability of this mutation. One of the possible causes of this could be the mutation´s heteroplasmy level. This project aimed to assess if there is a relation between the heteroplasmy level in three tissues and the phenotype. 3 families with a clinical diagnosis of MELAS and 2 families with a clinical diagnosis of MIDD were included. The presence and heteroplasmy level of the mutation were assessed via ARMS-qPCR on blood, urine and oral mucosa. One family with MELAS rendered positive for the m.3243AG mutation. A great phenotypic variation was found. The proposita had a greater heteroplasmy level in all 3 tissues compared to her oligosymptomatic relatives. The first Colombian patient with MELAS and the m.3271TC mutation is reported. These families were further analyzed.Maestrí

Case studies of two families with MIDD and MELAS: heteroplasmy level in m.3243A>G mutation and the first report on m.3271T>C mutation in Colombia

El síndrome MELAS (encefalomiopatía mitocondrial, acidosis láctica y episodios similares a isquemia cerebral) y el síndrome MIDD (diabetes y sordera de herencia materna) son enfermedades mitocondriales producidas en la mayor parte de los casos por una misma mutación: la m.3243A>G que afecta al gen MT-TL1. Se presentan los casos de dos familias con MELAS. En la primera se detecta la mutación m.3243A>G y se determina el nivel de heteroplasmia en sangre, orina y mucosa oral, con lo que se evidencia una gran variabilidad fenotípica: la paciente tenía una mayor heteroplasmia en los tres tejidos en comparación con sus familiares oligosintomáticos y la madre tenía una glicemia elevada e hipoacusia, sugiriendo un fenotipo cercano al MIDD. En la segunda familia se detecta la mutación m.3271T>C, siendo el primer caso reportado en Colombia. Estos hallazgos sugieren que el MIDD y el MELAS, descritos frecuentemente como entidades distintas, hacen parte de una misma entidad con expresividad variable dependiendo en parte de la heteroplasmia.MELAS syndrome (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes) and MIDD syndrome (maternally inherited diabetes and deafness) are mitochondrial diseases caused in most cases by the same mutation m.3243A> G, which affects the gene MT-TL1. The cases of two families with MELAS are presented here. In the first case, the m.3243A>G mutation was detected and the heteroplasmy level in blood, urine and oral mucosa were determined, finding a great phenotypic variability: the patient had higher heteroplasmy in the three tissues compared against oligosymptomatic relatives, and the mother had high blood sugar levels and hearing loss, suggesting a phenotype near to MIDD. In the second family, the m.3271T>C mutation was detected, which constitutes the first case reported in Colombia. These findings suggest that MIDD and MELAS, often described as distinct entities, are part of the same entity with variable expressivity partially depending on heteroplasmy

Case studies of two families with MIDD and MELAS: heteroplasmy level in m.3243A>G mutation and the first report on m.3271T>C mutation in Colombia

MELAS syndrome (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes) and MIDD syndrome (maternally inherited diabetes and deafness) are mitochondrial diseases caused in most cases by the same mutation m.3243A> G, which affects the gene MT-TL1. The cases of two families with MELAS are presented here. In the first case, the m.3243A>G mutation was detected and the heteroplasmy level in blood, urine and oral mucosa were determined, finding a great phenotypic variability: the patient had higher heteroplasmy in the three tissues compared against oligosymptomatic relatives, and the mother had high blood sugar levels and hearing loss, suggesting a phenotype near to MIDD. In the second family, the m.3271T>C mutation was detected, which constitutes the first case reported in Colombia. These findings suggest that MIDD and MELAS, often described as distinct entities, are part of the same entity with variable expressivity partially depending on heteroplasmy