Master Acute Intermittent Porphyria (AIP) with Picmonic for Medicine

Acute intermittent porphyria is inherited in an autosomal-dominant pattern. Therefore, patients only need one mutated gene to inherit the disease.

In acute intermittent porphyria, patients inherit an inhibiting mutation in porphobilinogen deaminase, which converts porphobilinogen into hydroxymethylbilane. In contrast, uroporphyrinogen decarboxylase converts uroporphyrinogen III to coproporphyrinogen III, and is the enzyme mutated in porphyria cutanea tarda.

Because porphobilinogen deaminase is inhibited, serum porphobilinogen and delta-ALA build up, as they are synthesized upstream from porphobilinogen deaminase. Urinary porphyrins are also increased, as they spill from the blood to the urine.

Because porphobilinogen deaminase is inhibited, serum porphobilinogen and delta-ALA build up, as they are synthesized upstream from porphobilinogen deaminase. Urinary porphyrins are also increased, as they spill from the blood to the urine.

Because porphobilinogen deaminase is inhibited, serum porphobilinogen and delta-ALA build up, as they are synthesized upstream from porphobilinogen deaminase. Urinary delta-ALA and porphobilinogen are also increased, as they spill from the blood to the urine.

Patients with acute intermittent porphyria have symptom flares precipitated by various triggers such as cytochrome P450 inducers, alcohol and starvation. Symptoms may include severe abdominal pain, port wine-colored urine, polyneuropathy and CNS symptoms and psychiatric disturbances.

Colicky epigastric abdominal pain is typically the presenting sign of an AIP flare. It lasts for several days and is often associated with nausea, vomiting and constipation.

During attacks, patients may experience polyneuropathy and other neurological symptoms; such as ascending weakness, seizures and cortical blindness.

Patients may experience psychological disturbances such as depression during attacks. They are also at increased risk for certain psychiatric diseases such as bipolar disorder and schizophrenia.

During flares, patients may have port wine-colored urine; initially the urine is colorless, but exposure to light causes the urine to change its color.

Glucose and hemin are the mainstays of treatment for AIP attacks. Hemin is a heme-containing porphyrin that comes as an IV solution. Both glucose and hemin inhibit ALA synthase, which is the first step in the heme synthesis pathway. By administering these two inhibitors, porphyrins are unable to build up and cause the classic symptoms of an AIP attack.

Acute intermittent porphyria is triggered by alcohol, starvation and cytochrome P450-inducing drugs including barbiturates, carbamazepine and rifampin. Therefore, patients should avoid these to prevent disease symptoms.