Focal dystonia caused by Mohr–Tranebjaerg syndrome with complete deletion of the DDP1 gene

Mohr–Tranebjaerg syndrome (MTS) is an X-linked hereditary disorder, characterized by childhood onset of sensorineural hearing loss, dystonia, mental retardation, behavioral disturbances, visual loss, and spasticity,1 due to mutations in the deafness–dystonia peptide-1 gene ( DDP1 ).2 Most DDP1 mutations cause protein truncation. We describe a 24-year-old man with MTS and an X-chromosome microdeletion involving the whole DDP1 gene as well as the Bruton tyrosine kinase ( BTK ) gene, responsible for X-linked agammaglobulinemia (XLA). In this patient, MTS predominantly manifested with severe deafness and visual loss, while the other cardinal features of the syndrome, mental retardation and movement disorders, were unusually mild. A 24-year-old man was referred because of writing difficulties. His mother had type I diabetes mellitus without neurologic complications. The patient had been full term, delivered after a normal pregnancy. At age 2 years, bilateral hearing loss appeared and recurrent infections led to a diagnosis of Bruton agammaglobulinemia. At age 15, a progressive visual loss was noticed. At age 19, the patient began to complain of writing difficulties …