<unk>  has an autosomal dominant pattern of inheritance. Mutations in the PPOX gene cause<unk> . The PPOX gene makes a membrane bound mitochondrial enzyme called protoporphyrinogen oxidase, which is critical to the chemical process that leads to heme production. The activity of this enzyme is reduced by 50 percent in most people with<unk> . In severe cases that begin early in life, the enzyme is almost completely inactive. Nongenetic factors such as certain drugs, stress, and others listed above can increase the demand for heme and the enzymes required to make heme. The combination of this increased demand and reduced activity of protoporphyrinogen oxidase disrupts heme production and allows byproducts of the process to accumulate in the liver, triggering an acute attack.<unk>  is inherited in an autosomal dominant pattern, which means the defective gene is located on an autosome, and inheriting one copy of the defective gene from an affected parent is sufficient to cause the disorder. More severe cases result from inheriting two copies of the defective gene. The entire PPOX gene has about 8kb with 13 exon sequences. It was successfully cloned from a cDNA library in 1995 revealing that, after processing, it is 477 nucleotides long. It has previously been thought that the PPOX gene was located on human chromosome 14, however mapping experiments (FISH) have shown that it is near 1q23. An additional aggravating mutation affecting<unk>  can be found at 6p21.3 on the HFE gene. A 2006 clinical, biochemical and mutational study of eight Swiss<unk>  patients and their families found four novel PPOX gene mutations believed to be unique to the Swiss population.
Variegate porphyria
Hepatic porphyria
Acute intermittent porphyria
Erythropoietic porphyria
Hepatoerythropoietic porphyria
Porphyria cutanea tarda
Porphyria
Harderoporphyria