Reversible dementia: a case of cryptococcal meningitis masquerading as Alzheimer's disease.

A 70-year-old man presented to us in 1994 with a three-year history of worsening dementia. With the exceptions of a Mini-Mental State exam score of 20 and an inability to tandem walk, his physical and neurological examinations were normal. His past medical history revealed that in 1992 he had been evaluated at another institution for memory impairment and bifrontal headaches. A spinal tap had been done in 1992 showing elevated protein, reduced glucose, and a pleocytosis; his CSF fungal culture and cryptococcal antigen test were negative. He subsequently was lost to follow-up, and although his headaches had resolved, his mental status had continued to worsen. In 1994 his CSF cryptococcal antigen was positive, and his CSF fungal culture grew C. neoformans. He gradually improved with treatment for cryptococcal meningitis (CM). With the exception of mild memory impairment, in 2003 he and his family thought that his mental status had returned to normal. This case emphasizes that: 1) CM should always be kept in the differential diagnosis of dementia; 2) CM may be extremely insidious and difficult to diagnose; and 3) if one is to rule out unequivocally all possible reversible causes of dementia, one should perform a spinal tap.