What is the gene product associated with Vitamin D-resistant rickets?

• A. Metallopeptidase
• B. Methyl-CpG-binding protein-2
• C. NF-B essential modulator
• D. Unknown

Answer: (A)

Vitamin D-resistant rickets, also known as hypophosphatemic rickets, is primarily associated with mutations in the PHEX gene. The gene product from the PHEX gene is a metalloproteinase, which plays a critical role in phosphate regulation. This dysfunction leads to impaired phosphate reabsorption in the kidneys and bones, causing the characteristic rickets symptoms.

The association with metalloproteinases is significant because they are involved in the metabolism of proteins and the regulation of bone mineralization. The specific metallopeptidase that is linked to rickets affects how phosphorus is processed in the body, highlighting the importance of this enzyme in maintaining proper mineral balance.

The other options listed do not directly relate to Vitamin D-resistant rickets. Methyl-CpG-binding protein-2 and NF-B essential modulator have distinct roles in gene regulation and immune response, respectively, and are not implicated in the pathophysiology of rickets. The designation of "unknown" would imply a lack of understanding about the genetic factors involved, which is not the case here, as the connection between the relevant metallopeptidase and rickets is well-established. Thus, the correct choice reflects the actual genetic basis responsible for this condition.