Holmes Tremor‐Like Phenotype in DYT1 Dystonia

Abstract

Holmes tremor is characterized by a combination of a flexion‐extension resting postural and action tremor, most often due to mesencephalic lesions affecting the nigrostriatal and cerebello‐thalamo‐cortical pathways. On the other hand, dystonic tremor represents a jerky postural and action tremor, which if severe enough may include a resting component and may arise from cerebellar and nigrostriatal dysfunction. Here, we present a patient with a four‐decade history of progressive tremor, initially interpreted as Holmes tremor with a dystonic (pseudospastic) gait, in whom whole exome sequencing (WES) demonstrated a pathogenic TOR1A deletion. This case highlights two important clinical points, (1) the need for proper semiologic interpretation: direct DYT1 testing could have been entertained if tremor was properly categorized as dystonic rather than cerebellar at the outset; and (2) the phenotypic variability of DYT1 dystonia, with tremor as a presenting and disabling feature separate from the body part affected by dystonia (“tremor associated with dystonia”).