Late Phase Porphyria Cutanea Tarda
This was a toughie for a lot of you, and so I will describe what I see which, in my mind, are the critical cues for making the correct diagnosis. What I see are multiple erosive-looking scars on the dorsum of the hand, with a milium on the fourth digit. Any time I see any changes, either blisters (which I rarely see) or exaggerated aging, which I commonly see, or scarring, as above, I think the patient has PCT or pseudoporphyria until proven otherwise.
As you all know, PCT has a predilection for the dorsal hands and, along with other findings of PCT (name three for three bonus points) is a marker for internal disease. Usually, it is associated with an underlying condition, with hemochromatosis and alcoholic cirrhosis being common factors, but by way of pathogens, Hep C and HIV are the usual suspects.
Why wasn't this LP? Well, I have seen LP just about everywhere, but the dorsal hands are not a really common location. I like the wrists, legs, lower back, nuchal scalp, etc., but dorsal hands, not so much. So, once again, if you see changes on the dorsal hands, think PCT.