So I have a sploty, Brown birthmark on my upper thigh, and I just remembered that I wasnt born with it. So I researched it and birthmarks can develop but, up to a month after birth. But the birthmark I have I got when I was about three months old. My mom told me that she , someone who went to medical school, was scared and didnt what it was or where it came. When I first got it it was purple and blue like a bruise, but then after a little while it turned brown. And Im confused as to why this happened, so if anyone knows or had an idea please let me know.
It sounds very much like a " lentigo simplex ". These tend to arise in childhood and never go away. I have one on my own arm. They are benign lesions that don't cause medical problems. They aren't magically related.
That being said, identifying skin lesions can be difficult for anyone other than a trained dermatologist. If you have concerns about this particular mark you might have a dermatologist look at it and give you an accurate diaqnosis.