Mohr-Tranebjaerg syndrome

Mohr-Tranebjaerg syndrome (MTS) (formerly DFN-1) is an X-linked neurodegenerative syndrome.^[1]

• Prelingual or postlingual sensorineural hearing loss
• Progressive dystonia and visual impairment
• Psychiatric symptoms, cognitive impairment and behavioural problems

Early-onset deafness is the only pathognomonic symptom; all other clinical signs vary in their degree of severity and clinical course.

• The underlying genetic defects are found in the TIMM8A/DDP1 gene located on chromosome Xq22.
• DDP1/TIMM8A encodes a small polypeptide of 97 amino acid residues, the deafness-dystonia peptide 1 (DDP1). Functional studies revealed that DDP1 is localized to the mitochondria, and plays a role in the import of nuclear-encoded preproteins into the mitochondrial inner membrane.
• Loss of DDP1 leads to impairment of specific mitochondrial functions and, subsequently, to degeneration of neuronal cells.

As with other mitochondrial disorders, there is no specific treatment for MTS.

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