Photosensitivity is also found in some of the porphyrias. EPP is considered one of the least severe of the porphyrias. It is the most common of the acute porphyrias. Patients with acute hepatic porphyrias should be monitored for HCC. AIP is one of the four porphyrias that presents as an acute attack. The links between porphyrias and mental illness have been noted for decades. Treatment of the acute symptoms of HCP is the same as for other acute porphyrias. HCP can be distinguished from most other acute porphyrias by the cutaneous findings. Subtypes of porphyrias depend on which enzyme is deficient. All other porphyrias are either skin- or nerve-predominant. Several European studies have linked the inherited hepatic porphyrias with a predisposition to hepatocellular carcinoma. Overall, the incidence of all porphyrias is estimated at 1&colon;20,000 in the United States. Like other porphyrias, AIP is more likely to present in women. The porphyrias are generally considered genetic in nature. In erythropoietic porphyrias, the enzyme deficiency occurs in the red blood cells.