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Título

Childhood-onset Myotonic Dystrophy type 1: A Case Report

RESUMO

Case Report
Thirteen year old girl with cramps and pain on both hands that initiated during early childhood and got worse after coronavirus disease 2019 (COVID-19) in november of 2020. She had myotonic phenomena at both hands and tongue, mild proximal weakness on both hip flexors and hip extensors, and a myopathic gait. No history of neurologic or genetic disorders in the family was reported.
Laboratory investigation of nutritional deficiencies, endocrine and other systemic involvement was negative. Electromyography showed myotonic myopathy. Genetic testing helped conclude the diagnosis of Myotonic Dystrophy type 1 (DM1).

Discussion
DM1 is the result of a CTG repeat expansion in the 3′ untranslated region of the DM1 protein kinase (DMPK) gene on chromosome 19q13.3.
The clinical triad associated with DM1 is myotonia, distal weakness and early-onset cataracts. Patients may refer to myotonia as cramps, muscle stiffness or delayed muscle relaxation. Proeminent pain and proximal weakness are features most associated with Myotonic Dystrophy type 2 (DM2), although case reports with this presentation in DM1, such as our patient, have been previously reported.
Childhood-onset of DM1 is characterized by symptoms initiated between after the completion of the first year of life to ten years old. A childhood-onset is more linked to intellectual impairment and gastrointestinal symptoms, such as diarrhea, constipation and fecal incontinence. Common adult features of myotonia do not present until early adolescence.
Our patient describes that pain and cramps got worse after coronavirus infection in 2020 and that was what motivated the family to search for medical counseling. At our best knowledge, there are no reports of worsening Myotonic Dystrophies after coronavirus infection. But patients with DM1 may be at higher risk for presenting severe acute respiratory syndrome (SARS) associated with COVID-19.

Conclusion
DM1 is a genetic disorder with onset described between birth and early adulthood associated with three cardinal features (myotonia, weakness and early-onset cataracts). Proximal weakness and pain are not the most prominent symptoms in patients with DM1, although previously reported. Patients with childhood-onset are expected to have a more severe course than those with adult onset, and an early recognition of symptoms may lead to a better quality of life in these patients.

Palavras Chave

Dystrophy; Myotonic Dystrophy; Genetic