If you describe something as pernicious, you mean that it is very harmful. I did what I could, but her mother's influence was pernicious. very harmful or evil, often in a way that you do not notice easily (pernicieux, from perniciosus, from pernicies , from nex )
A severe anemia most often affecting older adults, caused by failure of the stomach to absorb vitamin B and characterized by abnormally large red blood cells, gastrointestinal disturbances, and lesions of the spinal cord. Slow-developing disease in which vitamin B12 (see vitamin B complex) deficiency impairs red-blood-cell production. It can result from a diet lacking in vitamin B12 or when intrinsic factor, a substance needed for intestinal absorption of B12, either is not produced by stomach cells or cannot bind to the vitamin. It causes weakness, waxy pallor, shiny tongue, and stomach, intestinal, and neurological problems. Its slow development can allow anemia to become very severe by the time of diagnosis. Monthly B12 injections into muscle soon reverses the anemia, but the injections must be continued for life
a chronic progressive anemia of older adults; thought to result from a lack of intrinsic factor (a substance secreted by the stomach that is responsible for the absorption of vitamin B12)
() From Middle English, from Old French pernicios, from Latin perniciosus (“destructive”), from pernicies (“destruction”), from per (“through”) + nex (“slaughter, death”)