When Deborah first starting doing things that alarmed us–repeating herself, getting into car accidents, perseverating about Mother Earth–my research was geared to finding out what was wrong and how we could fix it.  Once Deborah was diagnosed with Frontotemporal Dementia, FTD, I searched for ways to maintain the quality of her life while keeping her safe.

As Deborah grew more silent and infantile by the day, though, I found myself searching her face.  Blue eyes, the right one still drifting center when she tired.  Strong nose and jawline that used to photograph well.  Smile with a faint crowding of front teeth that a seventh grade retainer failed to correct.  The pieces were all there, but they no longer added up to the sister I knew.  Something deeper was missing from her face, an elusive quality that was as hard to pinpoint as the essence that separated the Masters from lesser portraits.

Deborah was alive, of course, but in a different way than she was before the FTD developed.  I wanted to understand what was happening to Deborah’s brain.  I wanted to know why her neurons began to die.

I scoured websites from the major FTD research institutions:  University of California, SanFrancisco; Harvard’s Massachusetts General; Johns Hopkins; Penn State.  I read about DNA, chromosomes and genes, crash courses in genetics.  I saw more references about what wasn’t known about FTD than what was.

With apologies to those readers who left high school biology with a better understanding of genetics than I, this is what I learned.

We are made of cells with blueprints–DNA–that tells our bodies how to grow and function.  Genes are the part of DNA that give instructions for making proteins.  Proteins are necessary for cells–for us–to survive.

Genes send these instructions using four different chemicals grouped in sequences.  Think of the chemicals as letters, the groups as words, and the sequences as sentences and you’ll get the picture.

Sometimes a gene will malfunction and send the wrong instruction to the cell.  Think of the malfunction as a typo that changes a word and meaning of a sentence.  The incorrect instruction may cause the cell to make the wrong kind of protein, or too much of the right kind of protein.  It may also cause the cell to shut down completely.  When a gene doesn’t work properly, it’s called a mutation.  In Penn Medicine’s guide, Understanding the Genetics of FTD, they say it best:   “Mutations are genetic spelling mistakes.”

FTD is caused when nerve cells in the frontal and temporal parts of the brain degenerate.  Scientists aren’t certain what causes these nerve cells to die, but when they autopsy brains of people suspected of having FTD (like Alzheimer’s, a definitive diagnosis can’t be made until the patient dies), they find abnormal build-ups of specific proteins, build-ups that may be caused by mutated genes.

What my research can’t tell me is why the genes in Deborah’s started mutating in the first place.  “Is it inherited?” people asked when they heard about Deborah’s disease.  I heard the rest of their question–Are you going to get it, too?–though they never said it out loud.

I looked at the statistical chances of Deborah having gotten FTD in the first place.  She didn’t fall into the 10% strong family history of FTD group because our parents and grandparents didn’t have it.  Then again, our father’s father and our mother’s mother both died before they might have shown symptoms of diseased brain cells.

She could have fallen within the 20-25% group with some family history of neurodegenerative (brain cell) disease because our first cousin and her mother both had Alzheimer’s.  Other aunts and uncles may have developed it as well, had they not died so young.

But I needed to believe Deborah was in the 60-70% class of FTD, the group called sporadic.  I needed to believe she was one of those people who got it out of the blue.  I needed to believe that just because my sister was hit by a meteor, doesn’t mean one is going to strike me, too.

No amount of speculation on my part, however, would change the following truth. Even if FTD had me in its radar, was at this very moment plotting to infiltrate my brain, I wouldn’t see it coming.

Small comfort.