Progressive multifocal leucoencephalopathy (PML) may pose a clinical and diagnostic dilemma. The patient may remain in a protracted psychotic state with negative symptoms, without overt features of dementia. The condition blends with catatonia, and eventually with akinetic mutism in a patient of AIDS in the absence of clinical evidence of an immunocompromised state. The present case report highlights the need for an in-depth clinical, biochemical and MRI assessment of patients with catatonia and akinetic mutism. Stupor of an 'akinetic mutism' pattern seems an important indication for HIV screening, particularly in high-risk patients.