Etiologically is the adverb that belongs with etiology: it means “when we are talking about the cause of a disease,” not the pain, the treatment, or how common it is. You meet it in medical papers and lectures. “The two illnesses look the same etiologically” means “if you look at what started them, they match.” Though actually, some academic writers stretch it to any kind of cause, not only illness — the cause of a social problem, say. That wider use is real, but it still sounds like a lab coat. Everyday English just says “because of” or “if we look at the cause.” It is a heavy, formal word; nobody uses it at the dinner table.

病因上；就病因而言