Dados do Trabalho

Título

DIAGNOSING AND MANAGING CONGENITAL MYOTONIAS IN CHILDREN: CASES REPORTS DUE TO SCN4A PATHOLOGIC VARIATIONS

Apresentação dos casos

We present two cases of congenital myotonia related to sodium channel pathologic variations - a rare etiology in the context of childhood weakness complaints. Case 1: A 2-year-old girl experienced episodes of ophthalmoparesis and appendicular weakness, each lasting a few hours and resolving spontaneously. Since then, she complained of difficulty pedaling and walking long distances. Neurological examination revealed mild hypertrophy of biceps and latissimus dorsi, along with paramyotonia in the hands. Case 2: A 6-years-old boy had intermittent episodes of left foot inversion, which improved spontaneously. Neurological examination showed myotonic phenomenon upon forearm and hand percussion, and upon eye opening and closing. Both underwent genetic panel testing for neuromuscular diseases, revealing heterozygous mutations in the SCN4A gene, case 1: [SCN4A chr17:63.943.825 G > A c.3938C>T (p.Thr1313Met)]; case 2: [SCN4A chr 17 c.4765G>A p.(Val 1589Met)], consistent with the phenotype of Von Eulenberg Disease (VED). For case 1, we prescribed Carbamazepine and Acetazolamide, resulting in good control of symptoms. The patient 2 did not present recovery with Carbamazepine, now is free of medication, doing physical exercises as tolerated.

Discussão

Channelopathies, a group of ion channel disorders, include conditions affecting chloride, sodium, calcium, and potassium channels, which can manifest as periodic paralyzes or congenital myotonia. The most common channel involved is chloride, but in these cases we figure out a rare mutation in sodium channels. VED is characterized by sodium channel mutations leading to paradoxical myotonia, primarily affecting the hands and facial muscles, and exacerbated by cold and fasting. Patients may progress to muscle weakness and have an increased risk of laryngospasm. Treatment may involve acetazolamide and symptomatic therapies to manage myotonia. In these related cases, patient 1 demonstrated good response with medications, but patient 2 didn't recover from symptoms with therapy, what’s not expected from literature review.

Comentários finais

Congenital myotonias should be considered in the differential diagnosis of childhood ambulation difficulties. Neurological assessments should include examination for myotonic phenomena. Upon confirming the diagnosis, appropriate treatment should be initiated to enhance patient quality of life.

Referências

MASRUHA, M. Neurologia Infantil: Fundamentos e Prática Clínica. 2ed. São Paulo, SP: Editora dos Editores Eireli, 2023.

Palavras Chave

Channelopathies; SCN4A; myotonia