Question

A 56-year-old man presents with fatigue, pallor, and abdominal pain. He reports memory loss and reveals that he works at a battery recycling plant. On examination, a noticeable foot drop in both lower extremities is seen. Laboratory testing shows elevated blood lead levels. Which enzyme is affected in the given scenario?

• A. Aminolevulinic acid (ALA) dehydratase
• B. Uroporphyrinogen III
• C. Uroporphyrinogen I
• D. Pyruvate dehydrogenase

Answer 1

The Correct Option is A

A 56-year-old man's symptoms of fatigue, pallor, abdominal pain, and foot drop, along with his occupational exposure as a worker in a battery recycling plant, suggest lead poisoning. His elevated blood lead levels further confirm this diagnosis. In lead poisoning, one of the key pathophysiological effects is the inhibition of specific enzymes involved in the heme synthesis pathway.

The critical enzyme affected in this scenario is Aminolevulinic acid (ALA) dehydratase. Lead acts as a potent inhibitor of ALA dehydratase, also known as porphobilinogen synthase, which catalyzes the conversion of aminolevulinic acid to porphobilinogen in the heme biosynthetic pathway.

Inhibition of ALA dehydratase by lead leads to the accumulation of its substrate, aminolevulinic acid (ALA), and interrupts the synthesis of heme. This disruption is responsible for the clinical manifestations such as neurological symptoms, anemia, and abdominal pain, as seen in this patient.