Sunny found a paper on frontal sub-cortical dementias that mentioned the presenilin gene:
 

Thanks so much, Iris!  I read the article cited and fortunately isn't part of my genetic mutation.  The mutation discussed affects very young onset.  For anyone interested, here is an exerpt of the cited report: 

"In this report, we present the clinical and pathological details of a kindred of four individuals with a novel missense mutation (V272A) of the presenilin 1 gene (PSEN1) that experienced a subcortical dementia. The age of onset of symptoms ranged 26-36-year old, with an age at death of 36-46 years. Initial symptom was a marked mood disorder, with prominent parkinsonism in one case. The neuropsychological study, as well as the neuroimaging and PET in the proband were concordant with a subcortical dementia. The cerebral pathology showed in this patient, aside from the classical lesions of Alzheimer disease, Lewy bodies in cortex and substantia nigra, and widespread subcortical neuritic lesions. This clinical pattern and pathology expands the clinical spectrum of familial Alzheimer's disease and compel to include mutations of PSEN1 gene in the genetic study of subcortical dementia." 

Jimenez-Escrig A, Rabano A, Guerrero C, et al. New V272A presenilin 1