Natural - performing or happening in a standard way; missing abnormalities or deficiencies; "it is the natural matter to occur"; "natural immunity"; "a grandparent's natural affection for a grandchild" An alternate technique to classify IMPA is as Key or secondary. Most important IMPA (also referred to as idiopathic IMPA) occurs https://lorenzonyuln.ampedpages.com/getting-my-pet-pain-relief-to-work-62821512