Pellagra Meaning - #7270

I recently came across the term pellagra, and I had never heard of it before. From what I read, it’s caused by a deficiency in niacin (vitamin B3), but I don’t understand how that leads to such serious health problems. What is the exact pellagra meaning, and why does niacin deficiency affect the body so severely? From what I read, pellagra is known for the "three Ds"—diarrhea, dermatitis, and dementia. But how does a simple vitamin deficiency cause such extreme symptoms? If someone has pellagra, do they experience all three symptoms at the same time, or can they develop gradually? How long does it take for niacin deficiency to lead to pellagra—is it something that happens quickly, or does it take months or years to develop? I also saw that pellagra used to be more common in populations that relied heavily on corn-based diets. Why does corn-based food contribute to niacin deficiency? If someone eats corn but also consumes other sources of niacin, does that lower the risk of developing pellagra? Are there any medical conditions that prevent the body from absorbing niacin properly, increasing the risk of this disease? Another thing I’m wondering about is whether pellagra can be reversed. If someone is diagnosed early, does taking niacin supplements immediately stop the symptoms, or does the body take time to recover? Can permanent damage occur, especially in cases where the disease has affected the brain? For those who have had pellagra or know someone who has, what were the first symptoms? Did treatment with niacin work quickly, or did recovery take a long time? I just want to understand more about pellagra meaning, its causes, and how to prevent it.