Can you pick the cause of this injury?

Without peeking further down this post take a few moments to consider what you think may have caused the patternation on the arm of this 24 yo man.
Is it from trauma?
Is it from contact with a plant?
Self-inflicted?
Some sort of burn?

OK, then read on.

The injury occurred to an electrician named Winston Kemp and here is his story:

I went outside to save my pumpkins. (I guess it was May 21.) After that, I was going back inside. I just know it struck in our neighbor’s backyard, and it was bright and loud. I didn’t feel anything. I just came back inside like nothing was wrong. Umm…my arm was sore. But I didn’t … I don’t think I saw any marks until 30, 45 … [it was] maybe an hour before I saw the marks. Didn’t seek medical help. There’s not too much else to it. I just watched it to make sure that it was alright. I don’t know. I just went about my normal life until [Daphne] got back here and started freaking out.

It was probably 4 or 5 in the evening. I didn’t know that it had happened. I don’t know, I wasn’t even sure that it was lightning, but that’s the only thing I figured it was. That’s the only thing I could have come in contact with that would have caused the marks. No, it didn’t hurt when it happened, I didn’t even know it happened. A few hours after it happened it really started to bother me. The next day it was bad. The blisters started forming; they were really big. I walked around the house without a shirt on. I didn’t go to work on Monday. I felt sick to my stomach, I’m not sure if that was an after effect of the lightning, though. The week after it happened it ached and burned and the blisters kept on getting bigger. When [Daphne] got home, [she] lanced the blisters to prevent them from busting while at work or sleeping.
I was trying to prevent entire pieces of skin ripping off. We were careful and wrapped it after lancing the blisters to prevent causing an infection. As it started to heal, it itched like crazy (like any burn). I used after-tanning lotion that [Daphne] gave me. Even now, almost a month later, I get random pains running down my arm that last for a few minutes; and my shirt irritates it. The skin is still irritated/tender.

The patterns you see on Winston’s arm are known as Lichtenberg Figures¹ or Lightning Flowers.
These fractal patterns are thought by some to be caused by the rupture of capillaries as the lightning discharge flashes over the surface of the body.
Others have hypothessed that they may in fact be caused as electrons shower over the skin during the strike.

No other electrical injury causes this sort of pattern and it is considered diagnostic of a lightning strike.

They are not considered to be thermal burns and usually disappear within 24 hours. Histological examination of Lichtenberg flowers reveals normal epidermis and dermis with focally extravasated red blood cells in the subcutaneous fat. This subcutaneous vascular congestion may explain the brown or erythematous coloration, but the rapid, non scarring resolution of the coloration remains a mystery. — ER Jedi.

Lichtenberg Figures may also be found burnt into grass, or forming patterns of fused soil (Fulgurites) in the area where the lightning struck.

You can read the whole of Winston’s story  as well as see some pictures that were taken a year later.

1. named after the German physicist Georg Christoph Lichtenberg, who originally discovered and studied them. [↩]