[citation needed] Some people with variegate porphyria have skin that is overly sensitive to sunlight (photosensitive).

Areas of skin exposed to the sun develop severe blistering, scarring, changes in pigmentation, and increased hair growth.

[citation needed] Rarely, the signs and symptoms of variegate porphyria can begin in infancy or early childhood.

[4] 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 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.

It has previously been thought that the PPOX gene was located on human chromosome 14,[5] however mapping experiments (FISH) have shown that it is near 1q23.