The phenotypic spectrum of DYT24 due to ANO3 mutations

Abstract

Genes causing primary dystonia are rare. Recently, pathogenic mutations in the anoctamin 3 gene (ANO3) have been identified to cause autosomal dominant craniocervical dystonia and have been assigned to the dystonia locus dystonia-24 (DYT24). Here, we expand on the phenotypic spectrum of DYT24 and provide demonstrative videos. Moreover, tremor recordings were performed, and back-averaged electroencephalography, sensory evoked potentials, and C-reflex studies were carried out in two individuals who carried two different mutations in ANO3. Ten patients from three families are described. The age at onset ranged from early childhood to the forties. Cervical dystonia was the most common site of onset followed by laryngeal dystonia. The characteristic feature in all affected individuals was the presence of tremor, which contrasts DYT24 from the typical DYT6 phenotype. Tremor was the sole initial manifestation in some individuals with ANO3 mutations, leading to misdiagnosis as essential tremor. Electrophysiology in two patients with two different mutations showed co-contraction of antagonist muscles, confirming dystonia, and a 6-Hz arm tremor at rest, which increased in amplitude during action. In one of the studied patients, clinically superimposed myoclonus was observed. The duration of the myoclonus was in the range of 250 msec at about 3 Hz, which is more consistent with subcortical myoclonus. In summary, ANO3 causes a varied phenotype of young-onset or adult-onset craniocervical dystonia with tremor and/or myoclonic jerks. Patients with familial cervical dystonia who also have myoclonus-dystonia as well as patients with prominent tremor and mild dystonia should be tested for ANO3 mutations. © 2014 The Authors. Movement Disorders published by International Parkinson and Movement Disorder Society

Genetics of Dystonia

“…The HUGO Gene Nomenclature Committee lists ANO3 as DYT23 but has no entry for DYT24. The latter is in line with a paper entitled "The phenotypic spectrum of DYT24 due to ANO3 mutations" by Stamelou et al [ 69 ]. Recently, the combination of linkage analysis with whole-exome sequencing led to identifi cation of ANO3 as a new cause of autosomal-dominant dystonia [ 68 ].…”

“…Recently, the combination of linkage analysis with whole-exome sequencing led to identifi cation of ANO3 as a new cause of autosomal-dominant dystonia [ 68 ]. The age at onset ranged from early childhood to the forties [ 69 ]. The clinical picture consisted of focal dystonia affecting the neck, laryngeal muscles, and upper limbs accompanied by 6-Hz dystonic tremor with or without superimposed myoclonus in some.…”

Estudo Genético nas Distonias Primárias: Recomendações do Grupo de Neurogenética do Centro Hospitalar São João

“…Deve ser oferecida a possibilidade de testar para a presença de mutações DYT-ANO3 (DYT24) aos doentes com distonia mioclónica DYT-SGCE negativa com história familiar de distonia cervical ou distonia com mioclonias, bem como aos doentes com tremor proeminente e distonia ligeira. [10][11][12] (recomendação do GNgen do CHSJ).…”

Writing tremor: Should we look for a TOR1A mutation?

“…Indeed, although dystonia gene-associated tremor is a classical concept, cases are very rare. Isolated head tremor (in the presence or the absence of dystonic posture of the neck) has been reported in families with an ANO3 mutation (DYT24) [4]. Upper limb tremor was described in a patient with an SGCE mutation [5].…”