Dementia with the onset before the age of 65 years is classified as early-onset dementia. Although uncommon, it has considerable impact on the lives of patients and care givers, alike. A substantial subset of patients may have underlying reversible causes. Yet, many, especially those of the very young may be initially misdiagnosed. A case of young woman with rapid mental decay is described here. She was finally diagnosed with gliomatosis cerebri (GC) involving only right frontal lobe. This atypical radiological feature of GC with primary presentation as memory loss needs special attention and clinicians should be aware of such conditions.