What causes nemaline myopathy 9 (NEM9)?

Updated: Mar 11, 2019
  • Author: Matthew Harmelink, MD; Chief Editor: Amy Kao, MD  more...
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Answer

An autosomal recessive mutation in Kelch-like family member 41 (KLHL41) can cause nemaline rod myopathy type 9. [25]  A severe phenotype due to a frameshift mutation presents with decreased fetal movements, breech presentation, arthrogryposis, and skeletal abnormalities. Death was before 3 months of age. In contrast, missense mutations result in mild to moderate weakness, contractures, and mild skeletal deformities with life into teenage years. Wheelchair and respiratory support are needed in some, but other patients remained ambulatory without assistive devices. [25]

Muscle pathology showed sarcoplasmic rods, EM evidence of severe myofibrillar disarray, and KLHL41 reduction or absence by immunostaining. Knockdown of KLHL41 diminished motor function, nemaline bodies, and myofibrillar disorganization. [25]


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