Published in:
Open Access
01-12-2023 | Magnetic Resonance Imaging | Case report
A novel variant in the tropomyosin 3 gene presenting as an adult-onset distal myopathy - a case report
Authors:
Zhiyong Chen, Monica Saini, Jasmine Shimin Koh, Gareth Zigui Lim, Nancy Jiaojiao Dang, Kalpana Prasad, Swee Hoon Koh, Karine Su Shan Tay, Ming Lee, Helen Lisa Ong, Yi Zhao, Ankit Tandon, Josiah Yui Huei Chai
Published in:
BMC Neurology
|
Issue 1/2023
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Abstract
Background
We report a patient with a novel c.737 C > T variant (p.Ser246Leu) of the TPM3 gene presenting with adult-onset distal myopathy.
Case presentation
A 35-year-old Chinese male patient presented
with a history of progressive finger weakness. Physical examination revealed
differential finger extension weakness, together with predominant finger
abduction, elbow flexion, ankle dorsiflexion and toe extension weakness. Muscle
MRI showed disproportionate fatty infiltration of the glutei, sartorius and
extensor digitorum longus muscles without significant wasting. Muscle biopsy and
ultrastructural examination showed a non-specific myopathic pattern without
nemaline or cap inclusions. Genetic sequencing revealed a novel heterozygous
p.Ser246Leu variant (c.737C>T) of the TPM3 gene which is predicted to
be pathogenic. This variant is located in the area of the TPM3 gene
where the protein product interacts with actin at position Asp25 of actin.
Mutations of TPM3 in these loci have been shown to alter the sensitivity
of thin filaments to the influx of calcium ions.
Conclusion
This report further expands the phenotypic
spectrum of myopathies associated with TPM3 mutations, as mutations in TPM3
had not previously been reported with adult-onset distal myopathy. We also discuss the interpretation of variants
of unknown significance in patients with TPM3 mutations and summarise
the typical muscle MRI findings of patients with TPM3 mutations.