What is the mortality and morbidity associated with congenital myopathies?

Updated: Mar 11, 2019
  • Author: Matthew Harmelink, MD; Chief Editor: Amy Kao, MD  more...
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Given the wide spectrum of disease, the largest cause of morbidity and mortality is related to muscle function loss resulting in respiratory and/or feeding failure.

According to the study by Colombo et al., at birth, neonates with congenital myopathy required respiratory support and nasogastric feeding in 30.4% and 25.2% of cases, respectively. Of note, in the study cohort 12% of patients died within the first year, whereas 74.1% achieved independent ambulation with 62.9% being late walkers. [5]

Phenotype can vary greatly even in a single gene or pathologic classification. As such, consideration for the specific etiology is needed. Additionally, many infants/neonates with congenital myopathy can make improvements in the first few years of life. This makes early decisions regarding long-term goals of care, such as use of supportive care, difficult.  

However, after this initial gain, a small group can decline. The Colombo et al. cohort demonstrated this in the 9% of patients who were ambulatory but lost the ability. [5] While this can be from the primary pathologic process, this may also be related to a relative weakness in the context of a growing child with disproportionate needs for strength as compared to what their muscles can produce and may not be objective worsening weakness.

Other morbidities include extra-muscular features or risks. Most noticeably is the risk for malignant hyperthermia. While this is best described in a subset of patients with RYR1 mutations, there are other myopathic and dystrophic genes that can also be causative. There are also non-myopathic phenotypes of these genes that can have non-weak presentations.

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