This case study describes a 59-year old male patient who presented in November 2010 with an extrapyramidal clinical picture typical of corticobasal syndrome (CBS), but was later found to have a diagnosis of progressive multifocal leukoencephalopathy (PML). Presentation with CBS is atypical of PML, though it has been reported before: this is the sixth case recorded of an extrapyramidal presentation of the disorder. CBS is associated with the pathological diagnosis of corticobasal degeneration (CBD), which is difficult to confirm without a histological sample, as there is a low sensitivity for diagnosis of CBD in the clinic. This patient had undergone heart transplantation in 1998—subsequent to a ventricular free wall aneurysm after myocardial infarction—and was on an immunosuppressive regimen of Mycophenolate Mofetil (MMF) and Ciclosporin. PML is known to affect patients with organ transplants, and has successfully been managed by stopping immunosuppressive medications in renal transplant recipients. However, in the case of a heart transplant recipient, it was thought that the total cease of these drugs would have fatal consequences. Instead, Ciclosporin administration was continued but reduced, the MMF was stopped, and treatment was begun with Mefloquine and Mirtazapine. Unfortunately, the patient continued to deteriorate and passed away a few weeks after leaving hospital. There was no postmortem. PML has been reported before in heart transplant recipients, but this is the first recorded case of an extrapyramidal presentation in this patient group. This case reinforces the importance of considering PML in patients presenting with atypical clinical features, especially in transplant recipients, and highlights the question of management of these patients.