Reversible subacute chorea caused by nutritional deficiency

<h3></h3> We present a case of a 70-year-old lady with a six weeks history of progressive encephalopathy with visual hallucinations and choreiform movements of the right upper and lower limbs. Her past medical history included a longstanding eating disorder, Vitamin B12 deficiency, and several falls resulting in fractures. On examination, there was a right sided hemichorea with orofacial dyskinesia. Her speech was tangential and confabulatory. The remainder of the examination was normal. She scored 18/30 on Montreal Cognitive Assessment (MOCA). Investigations demonstrated a macrocytic anaemia with a low serum folate. Vitamin B12 was at the lower end of normal (287 pg/ml) with a raised homocysteine (indicating functional deficiency). MRI brain and cord was normal. CSF examination was unremarkable with the exception of CSF specific oligoclonal bands (not present on repeat testing). Extended autoantibody screening was negative with a negative CT CAP. She was treated with pabrinex, B12 injections, and folate replacement with complete resolution of her symptoms. On six month follow up, her cognitive improved with a score of 27/30 on MOCA. Although rare, B12 deficiency is a treatable cause of chorea that should not be missed.