A 56-year-old male with a history of liver transplant presented with progressive blindness and cognitive impairment over four months. MRI revealed patchy hyperintense T2/FLAIR signal within bilateral parieto-occipital subcortical white matter and posterior thalami. These features were suggestive of PRES, presumably secondary to Tacrolimus, which was subsequently discontinued.
The patient returned a month later with progressive symptoms. The neurological exam was consistent with confusion, cortical blindness, left motor apraxia and left hemineglect. Repeat MRI-brain showed significant interval increase in the supratentorial FLAIR hyperintense signal involving areas beyond those seen on the initial MRI, with wispy enhancement in the left parietal region.
PRES remained the leading diagnosis, although differentials included CNS immune reconstitution inflammatory syndrome, PML, post-transplant lymphoproliferative disorder, primary CNS lymphoma, and opportunistic infection. CSF was positive for JCV PCR. Brain biopsy with nuclear staining confirmed the diagnosis of PML.