Abstract Mitochondrial diseases are multisystemic disorders characterized by an impairment of the mitochondrial respiratory chain. Diagnosis requires an approach that involves a high index of suspicion, molecular techniques and a careful selection of the tissue to be studied. Our goal was to develop and implement local strategies for diagnosing mitochondrial disorders, by standardizing procedures of molecular biology and nucleic acid sequencing. A prospective, analytical, observational study was conducted in a cohort of, a total of 82 patients with suspected mitochondrial disorder who were treated at our hospital between May 2008 and June 2019. We developed molecular diagnostic tools that included classical monogenic techniques and Next Generation Sequencing. We characterized the neurological and extra neurological manifestations noted in our cohort. Following the proposed algorithm, we obtained a molecular diagnostic performance of 54%, identifying mutations in 44 patients. mtDNA mutations were identified in 34 patients. Structural rearrangements in mitochondrial genome were found in 3 and 7 in nuclear genes, respectively. Our results confirm the utility of the proposed algorithm and the molecular tools used, as evidenced by a high diagnostic performance. This is of great value to a more efficient and comprehensive medical care of patients and families affected by mitochondrial disorders.

Machado-Joseph disease (MJD) is the most frequent dominantly inherited spinocerebellar ataxia. A marked phenotypic variability is a characteristic of this disorder that could involve non-cerebellar presentations. Based on several case reports describing pyramidal dysfunction as the main symptom at onset, a clinical form resembling hereditary spastic paraplegia has been proposed. We report here two further cases of MJD patients whose initial clinical presentation suggested hereditary spastic paraplegia, and a summary of the main findings of previously similar published reports. Our findings lent support to the proposal of a MJD subtype distinguished by a marked pyramidal dysfunction at onset, simulating a clinical picture of hereditary spastic paraplegia.

La ataxia espinocerebelosa tipo 3 o enfermedad de Machado-Joseph (SCA-3/EMJ) es la forma más frecuente de ataxia espinocerebelosa autosómica dominante. Se caracteriza por una marcada variabilidad fenotípica, pudiendo causar formas no cerebelosas de presentación. En base a algunos casos comunicados, se ha propuesto una forma de presentación clínica similar a la de una paraparesia espástica hereditaria, con la presencia de signos de disfunción piramidal predominantes como la manifestación clínica inicial. Presentamos dos nuevos casos de SCA-3/EMJ con un cuadro clínico inicial sugerente de paraparesia espástica hereditaria y una revisión de los casos clínicos similares previamente informados. Nuestros hallazgos apoyan la propuesta de un subtipo de SCA-3/EMJ caracterizado por la presencia de marcada disfunción piramidal como manifestación inicial, simulando un cuadro clínico de paraparesia espástica hereditaria.

A single nucleotide polymorphism (SNP) at position -376 of the tumor necrosis factor á gene (TNFA) has been associated with susceptibility to multiple sclerosis (MS) in Spain. However, no association was found in populations from the USA and The Netherlands. Here we investigate the association between the TNFA - 376A SNP and MS susceptibility in Argentinean patients with MS. The A/G genotype was found in 4.4% of patients (n=90) and in 4.8% of healthy individuals (n=84; p=0.92; odds ratio=0.93; confidence interval: 0.23- 3.84). Thus, no significant differences in genotype and allele frequencies were found between healthy individuals and patients with MS in Argentina.

Un polimorfismo de nucleótido único (SNP, por sus iniciales en inglés) en la posición -376 del gen codificante del factor de necrosis tumoral á (TNFA) ha sido asociado en España con un mayor riesgo a padecer esclerosis múltiple (EM). Sin embargo, esta asociación no fue encontrada en estudios hechos en poblaciones provenientes de los EE.UU. y Holanda. Aquí investigamos la asociación entre el SNP TNFA -376A y el desarrollo de EM en una población de pacientes argentinos con EM. El genotipo A/G fue encontrado en 4.4% de los pacientes (n=90) y en 4.8% de los controles sanos (n=84; p=0.92; odds ratio=0.93; intervalo de confianza: 0.23-3.84). En consecuencia, no encontramos diferencias en las frecuencias alélicas y genotípicas entre los sujetos enfermos y los controles sanos en Argentina.