Phoebe is dying of a wasting disease, and my readers want to know what that disease might be. Not one of the characters knows any more about it than is described in the story.
The same reader who would be upset if I fired a muzzle-loading musket twice without reloading wants me to name a disease that may not have been discovered, named, or described for another hundred years.
Some of my stores are set at a time when people still believed an imbalance of humors caused disease, and germ theory was in its infancy. By the late 19th century diagnosis was coming into its own. Doctors might be able to tell you what you had but they couldn’t cure or even treat it.
I am not sure if readers want an old fashioned name like Epizooty, or Kings Evil, or if they expect a more modern term like Crohn’s disease (named in 1938) or Diabetes Mellitus (described as early as 1425, but not treatable ‘til 1922), or even Anorexia Nervosa known in the 19th century as “fasting girls” or “the Brooklyn enigma.”
Since I write in close third person, I have to go with what my characters knew. Phoebe has been seen by several doctors who can’t agree on a diagnosis. What they do agree on is that it is sure to end in her death.
Balancing the reader’s need to know with an accurate historical presentation is a difficult line to walk.
What would you do if Phoebe were your character?