Ormand’s disease is:
**Core Concept**
Ormand's disease is a rare genetic disorder characterized by a deficiency of the enzyme L-gulonolactone oxidase (GULO). This enzyme is crucial for the synthesis of ascorbic acid (vitamin C) in the body. Individuals with Ormand's disease are unable to produce vitamin C endogenously, leading to a life-long requirement for dietary intake of this essential nutrient.
**Why the Correct Answer is Right**
The correct answer is related to the enzymatic deficiency responsible for Ormand's disease. GULO is a key enzyme involved in the final step of ascorbic acid synthesis in animals. The deficiency of this enzyme results in the inability to produce vitamin C, which is essential for various bodily functions, including collagen synthesis, iron absorption, and immune function. Patients with Ormand's disease require a diet rich in vitamin C to prevent scurvy and other related complications.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as Ormand's disease is not associated with a deficiency of the enzyme phenylalanine hydroxylase (PAH), which is responsible for phenylketonuria (PKU).
**Option B:** This option is incorrect as Ormand's disease is not caused by a mutation in the gene encoding the enzyme dihydrofolate reductase (DHFR), which is involved in folate metabolism.
**Option C:** This option is incorrect as Ormand's disease is not characterized by an excess of the hormone cortisol, which is involved in the stress response and glucose metabolism.
**Clinical Pearl / High-Yield Fact**
Ormand's disease is a rare genetic disorder that highlights the importance of dietary vitamin C intake in maintaining optimal health. Patients with this condition require a diet rich in vitamin C to prevent scurvy and other related complications.
**Correct Answer: D. GULO deficiency.**