**Core Concept**
The patient's symptoms are suggestive of a condition known as porphyria, a group of disorders characterized by the accumulation of porphyrins due to defects in the heme biosynthesis pathway. This pathway involves a series of enzyme-catalyzed reactions that convert succinyl-CoA and glycine into heme.

**Why the Correct Answer is Right**
The patient's symptoms, such as abdominal pain, tremors, and excessive sweating, are consistent with acute intermittent porphyria (AIP), a type of porphyria caused by a deficiency of the enzyme hydroxymethylbilane synthase (also known as porphobilinogen deaminase). This enzyme catalyzes the conversion of porphobilinogen to hydroxymethylbilane, a key step in the heme biosynthesis pathway. A deficiency of this enzyme leads to the accumulation of porphobilinogen and other porphyrin precursors, which are toxic to the nervous system and cause the symptoms seen in AIP.

**Why Each Wrong Option is Incorrect**
**Option A:** Uroporphyrinogen decarboxylase is another enzyme involved in the heme biosynthesis pathway, but its deficiency is associated with a different type of porphyria, known as porphyria cutanea tarda (PCT). PCT is characterized by skin blistering and photosensitivity, rather than the neurological symptoms seen in AIP.
**Option B:** Ferrochelatase is the final enzyme in the heme biosynthesis pathway, responsible for the incorporation of iron into protoporphyrin to form heme. A deficiency of ferrochelatase is associated with erythropoietic protoporphyria (EPP), a type of porphyria characterized by sensitivity to light and hemolytic anemia.
**Option C:** Aminolevulinic acid dehydratase (ALAD) deficiency is associated with a different type of porphyria, known as ALAD porphyria. This condition is characterized by mild symptoms, including neurological symptoms and urine discoloration.

**Clinical Pearl / High-Yield Fact**
The symptoms of porphyria can be triggered by a variety of factors, including hormonal changes, certain medications, and stress. It's essential for clinicians to be aware of these triggers and to consider porphyria in the differential diagnosis of patients with unexplained abdominal pain or neurological symptoms.

**Correct Answer:** D. Porphyobilinogen deaminase.