Mutations in the tropomyosin 3 (TPM3) gene are associated with autosomal dominant and recessive nemaline 1 (NEM1) myopathy, congenital myopathy with disproportionate muscle fibre types and cap myopathy.
This French-Chilean study reports the case of a 47-year-old man with polycythemia, restricted vital capacity and mild apnea/hypopnea syndrome, requiring non-invasive ventilation.
Various additional examinations were carried out:
- physical assessment: this revealed bilateral ptosis and facial paresis, with an arched high palate and retrognathia; global hypotonia and diffuse axial weakness, including weakness of the neck and upper and lower limb girdles and weakness of foot dorsiflexion.
- muscle imaging: whole body MRI showed diffuse fat replacement with a non-specific pattern.
- molecular analysis: a panel of 122 neuromuscular disorder genes NGS revealed heterozygous SUV c.709G>A (p.Glu237Lys) on exon 8 of TMP3.
- histological analysis: a biopsy of the deltoid muscle showed a new histological pattern combining a disproportion of fibre types and caps.
These results support the pathogenicity of the new TMP3 variant and extend the phenotypic range of TMP3-related congenital myopathy.
