Victoria Advocate (Internet / Print) 02/18/06 Today marks the beginning of National Porphyria Week, a period dedicated to raising awareness about this uncommon but diverse group of disorders, which can cause symptoms ranging from acute attacks of hallucinations to extreme sensitivity of the skin to light. Dr. Karl Anderson, American Porphyria Foundation advisor and University of Texas Medical Branch faculty member, said that there are about seven distinct, recognized forms of porphyria, affecting about 10 per 100,000 people. This would translate to about 2,000 people with porphyria living in Texas. Anderson said people living in different areas of the world or belonging to different ethnic groups have no better nor worse chance of developing porphyria. The most common form of porphyria is Porphyria Cutanea Tarda, or PCT, which is marked by blisters developing on sun-exposed areas of the skin, such as the hands and face, he said.