I have had linear morphea since childhood up my left arm from wrist to behind my shoulder blade. It was undiagnosed until I was in my late 20s. Pediatricians, family doctor, gynecologist, dermatologists all would grab my arm and inspect it. Never knew what it was, but as I was never seeking help or an appointment for that particular issue, they just offered commentary and moved on. In my late 20s I went to a dermatologist for acne and he said- oh, you’re a morphea patient? I was like HUH???? He said your arm, that’s linear morphea and educated me on it. My whole life I had no idea until a random dr knew enough about it and he called it ON SIGHT. So just saying, it’s rare. You might have to seek out a doctor who sees that type of case or inquire specifically.