Is porphyria progressive or lethal?

It can be. There are many forms of porphyria, some of which are rather mild and inconsequential, others of which are progressive and possibly lethal. If you suspect that you have porphyria, then you need to see your doc right away for diagnosis and treatment.
Porphyria. It depends on what type of porphyria we're talking about. Some porphyrias can be dangerous, and some can be hereditary so you need to be more specific about what type you're worried about so that you can get appropriate advice from your physicians. Lots of information can be found on the website for the american porphyria foundation at www.Porphyriafoundation.Com.