Familial dementia of frontal lobe type

To describe an unusual case of familial frontal lobe dementia (FLD) with probable spongiform encephalopathy (SE).

The patient's clinical presentation, neuropsychological test results, family history, and results on magnetic resonance imaging (MRI) and positron emission tomography (PET) scans, among other routine investigations, are described. His leucocyte deoxyriboneucleic acid (DNA) was isolated, and his Prp (prion protein) gene was amplified with the polymerase chain reaction and sequenced using the Sanger method.

Clinically, the patient had a presenile frontal lobe dementia. Four of the 8 members of the generation preceding the patient had presenile dementia. Autopsies performed on 2 of these cases revealed SE, and a pathological diagnosis of Creutzfeldt-Jakob disease (CJD) was made. One other member of that generation died of a limbic encephalitis, although the neuropathological findings were atypical. Sequencing of the patient's Prp gene did not reveal the abnormalities expected in a familial case of CJD. The results of other investigations were compatible with FLD but were not specific to a particular diagnosis.

This case is a novel type of SE. The patient presented clinically with FLD, but based on the family history and neuropathology, a diagnosis of prion dementia seems likely. There were no mutations found in the Prp gene, so it is possible that there are SEs caused by genes or other pathological processes unrelated to the Prp gene.