What are the accumulated substrates in acute intermittent porphyria?

What are the accumulated substrates in acute intermittent porphyria?

• A. Heme and bilirubin
• B. Porphobilinogen and ALA
• C. Coproporphyrin and uroporphyrin
• D. ALA and heme

Answer: (B)

In acute intermittent porphyria, the primary accumulated substrates are porphobilinogen (PBG) and aminolevulinic acid (ALA). This condition is caused by a deficiency in the enzyme porphobilinogen deaminase, which plays a key role in the heme synthesis pathway. When this enzyme is deficient, ALA and porphobilinogen build up because they cannot be converted into the subsequent products in the pathway. Porphobilinogen, along with ALA, is integral to the synthesis of heme, a vital component for various biological processes, including oxygen transport and enzymatic functions. The accumulation of these substrates is associated with the clinical symptoms observed in acute intermittent porphyria, which can include abdominal pain, neurological disturbances, and psychiatric symptoms. The presence of these excess metabolites is a diagnostic feature that can be identified through urine testing, particularly because they are excreted in increased quantities during an acute attack. While other options may reference substances related to porphyrin metabolism or other porphyrias, they do not correctly reflect the specific accumulations seen in acute intermittent porphyria. This condition uniquely presents with increased ALA and porphobilinogen levels, making this answer the most accurate.

In acute intermittent porphyria, the primary accumulated substrates are porphobilinogen (PBG) and aminolevulinic acid (ALA). This condition is caused by a deficiency in the enzyme porphobilinogen deaminase, which plays a key role in the heme synthesis pathway. When this enzyme is deficient, ALA and porphobilinogen build up because they cannot be converted into the subsequent products in the pathway.

Porphobilinogen, along with ALA, is integral to the synthesis of heme, a vital component for various biological processes, including oxygen transport and enzymatic functions. The accumulation of these substrates is associated with the clinical symptoms observed in acute intermittent porphyria, which can include abdominal pain, neurological disturbances, and psychiatric symptoms. The presence of these excess metabolites is a diagnostic feature that can be identified through urine testing, particularly because they are excreted in increased quantities during an acute attack.

While other options may reference substances related to porphyrin metabolism or other porphyrias, they do not correctly reflect the specific accumulations seen in acute intermittent porphyria. This condition uniquely presents with increased ALA and porphobilinogen levels, making this answer the most accurate.