Condition: Porphyria, Acute Intermittent

Acute intermittent porphyria (AIP) is a rare metabolic disorder that is characterized by deficiency of the enzyme porphobilinogen deaminase (PBG-D), also known as uroporphyrinogen I-synthase. This enzyme deficiency results in the accumulation of porphyrins or porphyrin precursors in the body.

These are natural chemicals that normally do not accumulate in the body. This enzyme deficiency by itself is not sufficient to produce symptoms of the disease (latent). Additional factors must also be present such as hormones, drugs and dietary changes that trigger the appearance of symptoms. Symptoms of AIP may include abdominal pain, constipation, and muscle weakness.

AIP is one of a group of disorders known as the porphyrias. The common feature in all porphyrias is the excess accumulation in the body of porphyrins or porphyrin precursors. Different types of porphyias are characterized by the accumulation of different types of porphyrin chemicals.

Porphyrias can also be classified into two groups: the “hepatic” and “erythropoietic” types. In the hepatic types of porphyria, porphyrins and related substances originate in excess amounts from the liver; in the erythropoietic types, they originate mostly from the bone marrow.

The porphyrias with skin manifestations are sometimes called “cutaneous porphyrias.” The “acute porphyrias” are characterized by sudden attacks of pain and other neurological symptoms. These acute symptoms may be severe and often rapidly appear. An individual may be considered latent if he or she has the characteristic enzyme deficiency but has never developed symptoms. There can be a wide spectrum of severity between the latent and active cases of any particular type of porphyria. The symptoms and treatments of the different types of porphyrias are not the same.