Cutaneous porphyrias actually make up six different types of the inherited disorder porphyria. In each, patients cannot produce enzymes that create heme, a component of red blood cells that delivers oxygen. Heme is made of chemicals called porphyrins, and they can accumulate when they aren't converted into heme. This lack of heme and accumulation of porphyrins lead to the symptoms of porphyria. Cutaneous porphyrias target the skin.
In cases of cutaneous porphyria, the patient's skin is extremely photosensitive. The skin develops redness, painful irritation and blisters after being exposed to sunlight for a very short period of time. The skin may also swell when exposed to sunlight, and can also darken abnormally [source: American Porphyria Foundation]. As a result, patients are strongly advised to avoid exposure to sunlight.
Children inherit the disorder from one or more of their parents. There are eight different enzymes that convert porphyrins to heme, and an inherited mutation on any of the genes that express these proteins can lead to porphyria.