In isolated tremor, investigate serum catecholamines if there are other symptoms of pheochromocytoma (ie, episodes of headache, sweating and/or tachycardia).54 Test for toxins when there is a history of exposure.53 In tremor combined with dystonia or a family history of movement disorders and cognitive or psychiatric symptoms, consider testing copper and iron metabolism (serum copper, ceruloplasmin, iron, ferritin) as this can point to Wilson disease55 or neurodegeneration with brain iron accumulation56 (particularly neuroferritinopathy). This evidence concerns the gene CP and Tremor.