Rosenthal’s syndrome is due to deficiency of
**Core Concept**
Rosenthal's syndrome, also known as familial hyperphosphatemic tumoral calcinosis, is a rare genetic disorder characterized by the deposition of calcium phosphate crystals in the skin and soft tissues. This condition is associated with hyperphosphatemia and elevated levels of 1,25-dihydroxyvitamin D.
**Why the Correct Answer is Right**
The underlying mechanism of Rosenthal's syndrome involves a mutation in the GALNT3 gene, which encodes a glycosyltransferase enzyme responsible for the proper modification of fibroblast growth factor 23 (FGF23). FGF23 plays a crucial role in phosphate homeostasis by regulating the levels of 1,25-dihydroxyvitamin D. In Rosenthal's syndrome, the defective GALNT3 enzyme leads to the accumulation of unmodified FGF23, which is resistant to degradation and causes an increase in 1,25-dihydroxyvitamin D levels, resulting in hyperphosphatemia and calcification.
**Why Each Wrong Option is Incorrect**
* **Option A:** The correct answer is not related to the deficiency of phosphate or a disorder characterized by hypophosphatemia.
* **Option B:** The correct answer is not related to the deficiency of parathyroid hormone (PTH) or a disorder characterized by hypoparathyroidism.
* **Option C:** The correct answer is not related to the deficiency of 1,25-dihydroxyvitamin D or a disorder characterized by vitamin D deficiency.
**Clinical Pearl / High-Yield Fact**
Rosenthal's syndrome is a rare genetic disorder that highlights the importance of proper FGF23 modification in phosphate homeostasis. It serves as a reminder that genetic mutations can lead to complex disorders affecting multiple physiological pathways.
**Correct Answer:** D. GALNT3 deficiency.