A family with nemaline myopathy type 6 caused by hseterozygous mutation (c.1222C>T) in the KBTBD13 gene in China: A case report.

Nemaline myopathy (NEM) is a congenital myopathy that typically presents with proximal muscle weakness and hypotonia. To date, 13 genes have been associated with NEM. The Kelch repeat and BTB domain‐containing protein 13 (KBTBD13) gene (KBTBD13)‐related NEM is a rarely reported condition, and not a single case has been reported in Asia. Here, we report the case of a mother and daughter in China with NEM caused by a mutation (c.1222C>T) in KBTBD13. Their shared clinical phenotype is symmetrical muscle weakness in the arms and legs with childhood onset. Muscle magnetic resonance imaging showed the unique replacement mode of muscle with fibro‐fatty tissue. Histopathological examination revealed the presence of fibers containing rod‐shaped structures in the cytoplasm or under the sarcolemma. DNA sequencing analysis detected a heterozygous mutation (c.1222C>T) in KBTBD13 in this family. A founder effect for the variant may exist in the Low Countries of Belgium and the Netherlands, and the mutation may be a hotspot mutation in Europe, as it has not been reported in Asia. Our case study expands the spectrum of KBTBD13‐related NEM. [ABSTRACT FROM AUTHOR]