A 50-year-old man presented with worsening, virtually lifelong, chorea and 
progressive behavioural disturbance, involving disinhibition and hoarding, over 
10 years. Clinical assessment revealed chorea, dysarthria, areflexia, an 
inappropriately jovial, impulsive manner and neuropsychological evidence of 
frontosubcortical dysfunction. Investigation results included an elevated 
creatine kinase, caudate atrophy and hypoperfusion, acanthocytes in the 
peripheral blood and the McLeod phenotype. DNA studies demonstrated a 
single-base deletion at position 172 in exon 1 of the XK gene, giving rise to a 
premature stop codon at position 129 in exon 2.