Epilepsias mioclónicas progresivas / Progressive myoclonic epilepsies

RESUMEN Las epilepsias mioclónicas progresivas (EMP) son enfermedades neurodegenerativas infrecuentes, clínica y genéticamente heterogéneas, caracterizadas por presentar mioclonías de acción, crisis epilépticas y deterioro neurológico progresivo. Afectan principalmente a niños y adolescentes. Su cuadro clínico inicial dificulta un adecuado diagnóstico diferencial con otras enfermedades neurológicas genéticas más frecuentes como la epilepsia mioclónica juvenil. Se sabe que la mayoría de mutaciones genéticas que causan estas enfermedades reflejan una herencia autosómica recesiva, con variantes dominante o mitocondrial de excepcional frecuencia. El diagnóstico tiene lugar cuando se identifican las mutaciones en un paciente con un cuadro clínico característico (como es el caso de la enfermedad de Unverritch-Lundborg o la EMP del Mar del Norte). Por otro lado, en algunos casos son más útiles la anatomía patológica (para la enfermedad de cuerpos de Lafora o la epilepsia mioclónica con fibras rojas rasgadas) o exámenes auxiliares específicos (vgr., ácido siálico en orina para Sialidosis). Es importante hacer el diagnóstico específico ya que ello permite un tratamiento genético definido para algunas de estas enfermedades. El manejo de las crisis epilépticas incluye el uso de valproato como fármaco de primera línea, en tanto que otros como zonisamida y levetiracetam constituyen una segunda línea; sin embargo, la falta de respuesta al tratamiento médico antiepiléptico es relativamente común. El pronóstico puede variar entre una enfermedad y otra, pero, por lo general, suele ser desfavorable conduciendo a discapacidad severa o muerte temprana.

SUMMARY Progressive myoclonus epilepsies (PME) are infrequent neurodegenerative disorders clinically and genetically heterogeneous cause, characterized by action myoclonus, seizures and progressive neurologic disability. They mainly affect children and teenagers. Its early clinical features make the differential diagnosis difficult with other, more frequent neurogenetic diseases such as juvenile myoclonic epilepsy. The majority of genetic mutations that lead to these diseases are known to be autosomal-recessive inheritance, with autosomal-dominant or mitochondrial inheritance being of exceptional frequency. The diagnosis is made when the mutations are identified in a patient with characteristic clinical features (like in the Univerritch-Lundborg disease or North Sea PME). On the other hand, in some cases pathological (vgr., for Lafora body disease or for Myoclonic epilepsy with ragged-red fibers) or specific laboratory test (such as sialic acid in urine for Sialidosis), are more useful. It is important to make as specific a diagnosis as possible because there are some genetically defined therapies for some of these diseases. The management of the seizures in these diseases includes the use of valproic acid as a first-line drug treatment, and other drugs like zonisamide and levetiracetam as second-line. However, the lack of response to antiepileptic drugs is not uncommon. Although the prognosis varies within diseases, it is generally unfavorable and may lead to disability or early death.

Identification of a Novel Homozygous Splice-Site Mutation in that Causes Progressive Myoclonus Epilepsy with or without Renal Failure / 中华医学杂志(英文版)

<p><b>Background</b>Progressive myoclonus epilepsies (PMEs) comprise a group of rare genetic disorders characterized by action myoclonus, epileptic seizures, and ataxia with progressive neurologic decline. Due to clinical and genetic heterogeneity of PMEs, it is difficult to decide which genes are affected. The aim of this study was to report an action myoclonus with or without renal failure syndrome (EPM4) family and summarize the clinical and genetic characteristics of all reported EPM4 patients.</p><p><b>Methods</b>In the present study, targeted next-generation sequencing (NGS) was applied to screen causative genes in a Chinese PME family. The candidate variant was further confirmed by cosegregation analysis and further functional analysis, including the reverse transcription polymerase chain reaction and Western blot of the proband's muscle. Moreover, literature data on the clinical and mutational features of all reported EPM4 patients were reviewed.</p><p><b>Results</b>The gene analysis revealed a novel homozygous splicing mutation (c.995-1G>A) of the SCARB2 gene in two brothers. Further functional analysis revealed that this mutation led to loss function of the SCARB2 protein. The classification of the candidate variant, according to the American College of Medical Genetics and Genomics standards and guidelines and functional analysis, was pathogenic. Therefore, these two brothers were finally diagnostically confirmed as EPM4.</p><p><b>Conclusions</b>These present results suggest the potential for targeted NGS to conduct a more rapid and precise diagnosis for PME patients. A literature review revealed that mutations in the different functional domains of SCARB2 appear to be associated with the phenotype of EPM4.</p>

Progressive Myoclonus Epilepsy Associated with Macular Cherry-Red Spots

Myoclonus, generalized epilepsy, and progressive neurological decline characterize progressive myoclonus epilepsy. A 25-year-old woman was admitted for the evaluation of seizure, progressive myoclonus and ataxic gait. Her symptoms had developed since she was 13 years old. She did not have facial dysmorphism, hepatosplenomegaly, or dementia. Fundoscopic evaluation revealed cherry-red spots in both macular regions. Biochemical assays of hexosaminidase A, beta-galactosidase, and neuraminidase in leukocytes and urine mucopolysaccharides were free of any abnormality. The patient might have an unknown type of lysosomal storage disease.