Steinert's myotonic dystrophy: a case report

Case presentation: 9-year-old female, born at term by vaginal delivery without complications. Referred to the neurologist due to learning difficulties and gait imbalance. She was born with mild hypotonia, presenting with difficulty in breastfeeding, but did not need any ventilatory support. She was diagnosed with congenital clubfoot which was successfully treated until the age of 2 years and 4 months. Extended screening for inborn errors of metabolism and karyotype did not show any abnormalities. Brain MRI showed hypoxia. Regarding developmental milestones, she walked and spoke her first words at 1 year and 6 months. She did not have any family history of neurological disorders. However, her mother has mild cognitive impairment. On physical examination, he was able to understand and respond to all requests but presented rhinophonia, mandibular hypotonia, mild bilateral and symmetrical palpebral ptosis, hyporeflexia in all limbs, diffuse muscular hypotonia with strength grade 4 distal and 5 proximal in the upper limbs and foot drop bilaterally with strength grade 1 and 2 to the extension of the right and left feet respectively, strength grade 4 in the rest of the lower limb muscles, without fasciculations. Also, bilateral flexor plantar reflex, a myotonic phenomenon to thenar region percussion, and bilateral scrambling gait. The mother had bilateral eyelid ptosis, mild frontal baldness, and a clear myotonic phenomenon on percussion of the thenar region and when closing her eyes. Molecular genetic testing was requested for myotonic dystrophy type 1 (DM1), DMPK gene expansion, which was positive.

Discussion: DM1, or Steinert's myotonic dystrophy, is an autosomal dominant disease caused by an expansion in the DMPK gene. It is the most common type of muscular dystrophy in adults, being a multisystem disease. In the vast majority of cases, the diagnosis of DM1 can be made clinically and confirmed with genetic tests. Detailed medical history, family history, and physical examination are crucial.

Final comments: The reported case highlights the importance of clinical detailing in the pediatric consultation in the presence of neurological symptoms, as well as a thorough family history investigation, especially under suspicion of syndromes with an autosomal inheritance pattern, such as Steinert's disease. Moreover, we emphasize the importance of genetic counseling in the management of patients affected by this condition.

 

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No conflict of interest has been declared by the author(s).

Publication History

Article published online:
18 September 2023