Fructose has been implicated in numerous inflammatory disease processes including eczema, psoriasis, arthritis, gout, ADHD, Alzheimer's, high blood pressure, type 2 diabetes, fatty liver disease, and autoimmune diseases like rheumatoid arthritis, thyroiditis, systemic lupus erythematosus, and insulin-dependent diabetes.
Fructose is absorbed differently from glucose in the intestinal tract.
Glucose stimulates the release of insulin from the pancreas. Fructose doesn't. Instead of insulin, cells use glut-5 transporter to move fructose into cells. Most cells only have very limited amounts of this transporter, so it's primarily cleared by the liver, where it's easily transformed either into fat or components that eventually increase blood lipids like triglycerides.
And, fructose has a toxicity factor beyond its caloric equivalent.