Spinal Muscular Atrophy: Review of a Child Onset Disease
Moisés A. Alatorre-Jiménez
Laboratorio de Desarrollo-Envejecimiento, Enfermedades Neurodegenerativas, Centro de Investigación Biomédica de Occidente, Instituto Mexicano del Seguro Social. Sierra Mojada 800, 44243, Guadalajara, Jalisco, México and Centro Universitario de Ciencias de la Salud (CUCS), University of Guadalajara, Guadalajara, Jalisco, México and Asociación Mexicana de Atrofia Muscular Espinal (AMAME), Guadalajara Jalisco, México.
Juan P. Sánchez-Luna
Laboratorio de Desarrollo-Envejecimiento, Enfermedades Neurodegenerativas, Centro de Investigación Biomédica de Occidente, Instituto Mexicano del Seguro Social. Sierra Mojada 800, 44243, Guadalajara, Jalisco, México and Asociación Mexicana de Atrofia Muscular Espinal (AMAME), Guadalajara Jalisco, México.
Erika D. González-Renovato
Laboratorio de Desarrollo-Envejecimiento, Enfermedades Neurodegenerativas, Centro de Investigación Biomédica de Occidente, Instituto Mexicano del Seguro Social. Sierra Mojada 800, 44243, Guadalajara, Jalisco, México and Centro Universitario de Ciencias de la Salud (CUCS), University of Guadalajara, Guadalajara, Jalisco, México.
Angélica L. Sánchez-López
Laboratorio de Desarrollo-Envejecimiento, Enfermedades Neurodegenerativas, Centro de Investigación Biomédica de Occidente, Instituto Mexicano del Seguro Social. Sierra Mojada 800, 44243, Guadalajara, Jalisco, México and Centro Universitario de Ciencias de la Salud (CUCS), University of Guadalajara, Guadalajara, Jalisco, México.
Sergio A. Sánchez-Luna
Department of Internal Medicine, University of Iowa Hospital and Clinics, Iowa, USA.
Vanessa E. Hernández-Navarro
Laboratorio de Desarrollo-Envejecimiento, Enfermedades Neurodegenerativas, Centro de Investigación Biomédica de Occidente, Instituto Mexicano del Seguro Social. Sierra Mojada 800, 44243, Guadalajara, Jalisco, México and Centro Universitario de Ciencias de la Salud (CUCS), University of Guadalajara, Guadalajara, Jalisco, México.
Fermín P. Pacheco-Moises
Centro Universitario de Ciencias Exactas e Ingenierías, University of Guadalajara, Guadalajara, Jalisco, México.
Genaro G. Ortiz *
Laboratorio de Desarrollo-Envejecimiento, Enfermedades Neurodegenerativas, Centro de Investigación Biomédica de Occidente, Instituto Mexicano del Seguro Social. Sierra Mojada 800, 44243, Guadalajara, Jalisco, México.
*Author to whom correspondence should be addressed.
Abstract
Spinal Muscular Atrophy (SMA) is a group of inherited disorders that involve mainly bulbar and spinal motor neurons; causing muscle weakness and atrophy of proximal and symmetrical predominantly in lower extremities, without affecting the facial muscles and the intellectual ability. It is also unclear if SMA is a developmental or a neurodegenerative disease and occurs predominantly in childhood. The continuous clinical spectrum of SMA has been divided into 3 types based on the age at onset and highest motor milestones achieved. SMA type I was described by Hoffman in 1894 and in 1900 was reported as a disease characterized by hypotonia during the first 3 months of life, as well, is considered as the leading cause of death in children under two years of age among genetic diseases worldwide. SMA type II patients can achieve sitting but not walking. While SMA type III patients achieve full milestones with a progressive loss of walking ability. Deterioration in muscle strength and motor function eventually occurs in SMA type II and III. SMA occurs due to depletion of SMN, a ubiquitously expressed protein, which in all cells regulates RNA biogenesis and splicing through its role in the assembly of small nuclear ribonucleoprotein (snRNP) complexes.
Keywords: Spinal muscular atrophy, survival motor neuron, SMN genes, child milestones, SMA types.