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Autoimmune diseases occur when the immune system destroys its own healthy tissues. When this occurs, white blood cells cannot distinguish between pathogens and normal cells.
Astigmatism is the most common vision problem. It may accompany nearsightedness or farsightedness. It is usually caused by an irregularly shaped cornea, but sometimes it is the result of an irregularly shaped lens. Either type can be corrected by eyeglasses, contact lenses, or refractive surgery.
Medication errors are more common among seriously ill patients than with those with minor conditions.
Multiple experimental evidences have confirmed that at the molecular level, cancer is caused by lesions in cellular DNA.
In 1864, the first barbiturate (barbituric acid) was synthesized.