Myotonic dystrophy - type 1

Case contributed by Kathryn Kinser

Presentation

Ex 37 week (ex 35 week by exam) baby girl born via C-section for maternal reasons. History of polyhydramnios. Profound hypotonia, poor sucking and swallowing at birth.

Patient Data

Age: 0 days
Gender: Female
X-ray

There are 12 pairs of ribs. The ribs are thin. The thorax is small and bell-shaped pronounced due to poor respiratory effort.

Feeding tube terminates in the stomach.

Cardiothymic silhouette appears enlarged due to low lung volumes and poor inspiratory effort and small thorax.  

Opacity in right upper and mid zone is most likely the thymus. No effusion or pneumothorax.

Non-specific non-obstructive bowel gas pattern is seen throughout the abdomen.

Symmetric abduction at the hips and well-positioned infant without restraining suggests diffuse hypotonia.

Comment:

Findings are highly suggestive of neonatal neuromuscular disease; differentials include: myotonic dystrophy, spinal muscular atrophy, myopathy among others.

 

Case Discussion

Given clinical and radiographic findings, this baby underwent typical diagnostic workup, which includes EMG, muscle biopsy/stain, genetic testing, etc. and was diagnosed with type I myotonic dystrophy.

The incidence of myotonic dystrophy is approximately 1/8000 people. Type I myotonic dystrophy is divided into different types. There are different classifications comprising of 3-4 different types, one classification characterized by age of onset and the other by severity.

Congenital myotonic dystrophy is the most severe form and usually associated with a greater number of trinucleotide repeats. Transmission is autosomal dominant with variable penetrance and expression. Prior to delivery, difficulty swallowing contributes to polyhydramnios and pregnancy may be complicated by preterm delivery. 

At birth or in the newborn period, infants can present with respiratory distress, hypotonia, and difficulty feeding. Patients can also exhibit developmental delay and failure to thrive. Gastrointestinal dysmotility is common and can predate later onset forms of myotonic dystrophy.

This case was submitted with supervision and input from:

Soni C. Chawla, M.D.
Associate Professor
Department of Radiological Sciences
David Geffen School of Medicine at UCLA
Olive View - UCLA Medical Center

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Case information

rID: 66131
Published: 11th Feb 2019
Last edited: 2nd Mar 2019
Inclusion in quiz mode: Included

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