Congenital myopathy

Gene: MT-TW

Red List (low evidence)

After NHS Genomic Medicine Service consideration, the rating of this gene has been updated to red. GLH review concluded that mitochondrial myopathies are not good fit for this panel. R300 Possible mitochondrial disorder - whole mitochondrial genome sequencing would be the more appropriate test.

Created: 11 Dec 2025, 5:32 p.m. | Last Modified: 11 Dec 2025, 5:32 p.m.

Panel Version: 6.43

Comment on list classification: As reviewed by Katherine Schon, myopathy has been reported in patients with m.5521G>A variant in MT-TW. However, there is no clear evidence for the onset of myopathy in infancy or early childhood. Hence, expert review is being sought on whether to promote this gene to green rating on this panel.

Created: 27 Jun 2025, 3:56 p.m. | Last Modified: 27 Jun 2025, 3:56 p.m.

Panel Version: 6.19

PMID:9673981 - The m.5521G>A variant in MT-TW gene was identified in a patient with late-onset mitochondrial myopathy.

PMID:20360171 - A female patient was reported with m.5521G>A variant, who initially developed sensorineural hearing loss at 24 years of age. She was diagnosed with overlapped MERRF/ MELAS phenotype.

PMID:23841600 - Three Tunisian patients were reported with mitochondrial myopathy. One of these patients was detected with m.5521G>A variant in MT-TW and with m.8682A>G variant in MT-ATP6 gene. This patient had the onset of the disorder at 11 months of age with neurodevelopmental and psychomotor delay, mental retardation, axial hypotonia, paraplegia, seizures and lactic acidosis. It is not clear when this patient started showing myopathic features.

Created: 27 Jun 2025, 3:37 p.m. | Last Modified: 27 Jun 2025, 3:51 p.m.

Panel Version: 6.16

Mode of inheritance
MITOCHONDRIAL

Phenotypes
inborn mitochondrial myopathy, MONDO:0009637

Publications

• 9673981
• 20360171
• 23841600

Green List (high evidence)

m.5521G>A pathogenic variant in MT-TW has been reported to cause mitochondrial myopathy.

Created: 24 Jun 2025, 10:53 a.m. | Last Modified: 24 Jun 2025, 10:53 a.m.

Panel Version: 6.10

Mode of inheritance
MITOCHONDRIAL

Publications

• 9673981
• 23841600

Mode of pathogenicity
Other