First Two Case Reports of Becker’s Type Myotonia Congenita in Colombia: Clinical and Genetic Features

Abstract

Background

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

Abbreviations

BTMC, Becker’s type Myotonia Congenita; DMPK, myotonic dystrophy protein kinase; DM1, myotonic dystrophy type 1; CIC-1, skeletal muscle chloride channel-1; DM2, myotonic dystrophy type 2; PROMM, proximal myotonic myopathy; HLA-I, human leukocyte antigen class I; CBS, cystathionine-beta-synthase; CMAP, compound muscle action potential.

Data Sharing Statement

All data generated or analysed during this study are included in this published article.

Ethics Approval and Consent to Participate

The study was assessed and supported by the biomedical ethics committee at Fundación Valle del Lili. All patients included in this descriptive study filled out the written informed consent. Additionally, written consent to publish this information was obtained from study participants.

Consent for Publication

All patients whose clinical or molecular data are used in this manuscript gave publication consent during their informed consent completion. Written consent for publication was obtained from the study participants.

Acknowledgments

We thank our patients for participating in the study.

Author Contributions

All authors made substantial contributions to conception and design, acquisition of data, or analysis and interpretation of data; took part in drafting the article or revising it critically for important intellectual content; agreed to submit to the current journal; gave final approval for the version to be published; and agreed to be accountable for all aspects of the work.

Disclosure

The authors declare that they have no competing interests.

Additional information

Funding

No funding of any kind or funding source was provided during the implementation and execution of this study.