Frontotemporal Lobar Degeneration and HHV-6
"Pick's disease, a type of frontal lobe degeneration, was first recognized clinically in 1892.1 However, frontal lobe degenerative dementia was considered rare until 1987 when 12.5% of autopsy cases from a series of patients with dementia were reported to have degeneration of the frontal lobes with non-Alzheimer's pathology.2 Since then frontotemporal lobar degeneration (FTLD) has become recognized as the third most common cause of cortical dementia behind Alzheimer's disease and Lewy body disease. In 1998 the consensus guidelines for the clinical diagnosis of FTLD were published." http://www.dcmsonline.org/jax-medicine/2000journals/February2000/ftld.htm
"Circumscribed cerebral atrophy of the frontal and anterior temporal lobes, also called lobar atrophy, is the gross pathological hallmark of FTLD." http://www.dcmsonline.org/jax-medicine/2000journals/February2000/ftld.htm
Contrary to conventional wisdom, FTLD may not be primarily a genetic disorder:
"In one study about 45% of FTLD patients have family members with a similar disorder.7 Genetic mutations in the tau protein on chromosome 17 have been identified in several families. Most of these mutations have been shown to increase the proportion of an isoform of tau called 4-repeat tau.8 However, it is clear that most cases in clinical practice don't have one of these mutations on chromosome 17. In fact in more than 50 consecutive cases, we have identified none with a chromosome 17 mutation. Apolipoprotein E4 allele (which has been shown to be a risk factor for AD) does not appear to be associated with FTLD." http://www.dcmsonline.org/jax-medicine/2000journals/February2000/ftld.htm