The Application of Clinical Genetics (Dec 2021)
First Two Case Reports of Becker’s Type Myotonia Congenita in Colombia: Clinical and Genetic Features
Abstract
Jorge Andres Olave-Rodriguez,1 Francisco Javier Bonilla-Escobar,2– 4 Estephania Candelo,5,6 Lisa Ximena Rodriguez-Rojas1,7 1Universidad Icesi, Faculty of Health Sciences, Cali, Colombia; 2Somos Ciencia al Servicio de la Comunidad, Fundación SCISCO/Science to Serve the Community, SCISCO Foundation, Cali, Colombia; 3Universidad del Valle, Cali, Colombia; 4Institute for Clinical Research Education, University of Pittsburgh, Pittsburgh, PA, USA; 5Centro de Investigaciones Clínicas, Fundación Valle del Lili, Cali, Colombia; 6Centro enfermedades raras y malformaciones congenitas (CIACER), Universidad Icesi, Cali, Colombia; 7Human Genetics Department, Fundación Valle del Lili, Cali, ColombiaCorrespondence: Lisa Ximena Rodriguez-Rojas Cra. 98 ## 18-49, Cali, Valle del Cauca, ColombiaEmail [email protected]; [email protected]: Becker’s type myotonia congenita is an autosomal recessive nondystrophic skeletal muscle disorder characterized by muscle stiffness and the inability of muscle relaxation after voluntary contraction. It is caused by mutations in the CLCN1 gene, which encodes for a chloride channel mainly expressed in the striated muscle. Most cases have been reported in the European population, and only mexiletine has demonstrated a randomized placebo-controlled, double-blinded effectiveness.Case Presentation: We present two male siblings from Colombia with Latino ancestry, without parental consanguinity, with myotonia during voluntary movements, muscle hypertrophy of lower extremities, transient weakness, and severe muscle fatigue after exercise from three years of age. A genetic panel for dystrophic muscle disorders and a muscle biopsy were both negative. Genetic testing was performed in their second decade of life. Both patients’ exomic sequencing test reported the mutation c.1129C >T (p.Arg377*) affecting exon 10 of the CLCN1, generating a premature stop codon. This mutation was described as pathogenic and observed in only one other patient in the United Kingdom.Conclusion: To our knowledge, these are the first cases of Becker’s type myotonia congenita reported in Colombia. Increasing awareness of healthcare providers for this type of disease in the region could lead to the identification of undiagnosed patients. Limited availability of medical geneticists as well as genetic testing may be the cause of the lack of previous description of cases, in addition to the delay in the diagnosis of the patients. Further epidemiological studies can reveal underdiagnosed myotonias in the country and in the Latin-American region.Keywords: Becker type myotonia congenita, myotonia congenita, Colombia, muscular diseases, siblings case reports
