Recurrent sore on leg

I have a recurrent itchy sore on my leg.
I have had it since I was 10 years old, and am now 37.
It starts at my ankle, and goes in a line halfway up my lower leg.
It used to run in this line all the way to my groin. I saw a dermatologist when i was a kid about it, and he was thrilled to see it from what I remember, saying it was very rare, even taking photos of it. He gave me an ointment, which I think was a cortizone. Ive tried it on my ankle since and have not had any luck.

It starts itching, and I scratch it till it bleeds. It then hurts while healing to a long lump, and itches like hell again.

Its very ugly, and I have another 18 months to go till I get to see the dermatologist through our state health system.

Anyone got any ideas?

Thanks