A novel homozygous exon2 deletion of TRIM32 gene in a Chinese patient with sarcotubular myopathy: A case report and literature review.

Sarcotubular myopathy (STM) is a rare autosomal recessive myopathy caused by TRIM32 gene mutations. It is predominantly characterized by the weakness of the proximal limb and mild to moderate elevation of creatine kinase (CK) levels. In this study, we describe a 50-year-old Chinese man who exhibited a proximal-to-distal weakness in the muscles of the lower limbs and who had difficulty standing up from a squat position. The symptoms gradually became more severe. He denied a history of cognitive or cardiological problems. The patient's parents and children were healthy. Histopathological examination revealed dystrophic changes and irregular slit-shaped vacuoles containing amorphous materials. Whole-exome sequencing consisting of protein-encoding regions of 19,396 genes was performed, the results of which identified one novel homozygous 2kb deletion chr9.hg19: g.119460021_119461983del (exon2) in the TRIM32 gene. This was confirmed at the homozygous state with quantitative real-time PCR. Here, we present a Chinese case of STM with one novel mutation in TRIM32 and provide a brief summary of all known pathogenic mutations in TRIM32.

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.

A case report: autosomal recessive Myotonia congenita caused by a novel splice mutation (c.1401 + 1G > A) in CLCN1 gene of a Chinese Han patient.

BACKGROUND: Autosomal recessive Myotonia congenita (Becker's disease) is caused by mutations in the CLCN1 gene. The condition is characterized by muscle stiffness during sustained muscle contraction and variable degree of muscle weakness that tends to improve with repeated contractions. CASE PRESENTATION: A 21-year-old man presented with transient muscle stiffness since the last 10 years. He had difficulty in initiating movement and experienced muscle weakness after rest, which typically improved after repeated contraction (warm-up phenomenon). There was no significant family history. Medical examination showed generalized muscle hypertrophy. Serum creatine kinase level was 2-fold higher than the normal value. Electromyogram showed myotonic discharges. DNA sequence analysis identified a novel splice mutation (c.1401 + 1G > A) and a known mutation (c.1657A > T,p.Ile553Phe). He rapidly responded to treatment with mexiletine 100 mg three times a day for 6 months. CONCLUSIONS: This case report of autosomal recessive Myotonia congenita caused by a novel compound heterozygous mutation expands the genotypic spectrum of CLCN1 gene.