Myotonic Dystrophy (DM)

Congenital-Onset DM1

Medical management

Babies born with congenital-onset DM1 have the most complex medical challenges seen in DM. Although the prognosis for these children has improved, the disease still has profound consequences and can be life-threatening, especially in the early months.

Breathing difficulties

The muscles needed for breathing are very weak in congenital-onset DM1, and a baby born with this disorder is likely to need a ventilator for an uncertain period of time. Respiratory involvement is the leading cause of death in the neonatal period. Need for support longer than four weeks usually indicates a poor prognosis for survival, and the mortality rate before the age of 18 months exceeds 25%.⁷ However, breathing muscles do generally become stronger over time.

Cognitive impairment

Cognitive impairment and intellectual disability are common in congenital-onset DM1, often requiring early intervention during the preschool years and special education later.

Feeding difficulties

Weakness in the muscles needed for sucking may impair a baby's ability to feed. Feeding difficulties are common during the first two years of life, and children with congenital DM1 are at increased risk for aspiration. Survivors usually are able to suck and swallow adequately for oral nutrition by 8 to 12 weeks of age. If the weakness is interfering with nutrition and hydration, a tube can be inserted either down the nose into the stomach (nasogastric tube) or directly into the stomach from outside (gastrostomy tube) until the muscles become strong enough for a child to eat and drink by mouth.

Muscle abnormalities

Babies with congenital-onset DM1 are born "floppy," with weak muscles and poor muscle tone. The medical term for this is hypotonia.

Motor milestones, such as sitting, standing, and walking, are likely to be delayed but ultimately are achieved by most children. Muscle weakness in the feet may cause the feet to be fixed in a downward-pointing, inward-turning position. This condition is known as clubfoot, or talipes equinovarus. This condition may have to be treated by casting or surgery before a child can walk.

To learn more about congenital DM1, read:

• Energy, Dedication, Hope Help Parents of Children with Congenital DM1
• On pregnancy, see Myotonic Dystrophy: A Special Case and the profile called Baby Born with Challenges
• The Brain in DM (see the section called Special education in congenital DM1)
• Building the IEP Puzzle: Tips for building effective IEPs and improving your child's educational experience

References

1. Lund, M. et al. Cardiac involvement in myotonic dystrophy: A nationwide cohort study. Eur. Heart J. (2014). doi:10.1093/eurheartj/ehu157
2. Logigian, E. L. et al. Mexiletine is an effective antimyotonia treatment in myotonic dystrophy type 1. Neurology (2010). doi:10.1212/WNL.0b013e3181dc1a3a
3. Meola, G. & Moxley, R. T. Myotonic dystrophy type 2 and related myotonic disorders. Journal of Neurology (2004). doi:10.1007/s00415-004-0590-1
4. Suokas, K. I., Haanpää, M., Kautiainen, H., Udd, B. & Hietaharju, A. J. Pain in patients with myotonic dystrophy type 2: A postal survey in Finland. Muscle and Nerve (2012). doi:10.1002/mus.22249
5. George, A., Schneider-Gold, C., Zier, S., Reiners, K. & Sommer, C. Musculoskeletal pain in patients with myotonic dystrophy type 2. Arch. Neurol. (2004). doi:10.1001/archneur.61.12.1938
6. Udd, B. & Krahe, R. The myotonic dystrophies: Molecular, clinical, and therapeutic challenges. The Lancet Neurology (2012). doi:10.1016/S1474-4422(12)70204-1
7. Reardon, W., Newcombe, R., Fenton, I., Sibert, J. & Harper, P. S. The natural history of congenital myotonic dystrophy: Mortality and long term clinical aspects. Arch. Dis. Child. (1993). doi:10.1136/adc.68.2.177