Question

A child presents with growth failure. Biochemical analysis shows normal Ca2+, normal PTH, reduced phosphate, and increased ALP. What is the diagnosis? 

• A. Nutritional rickets
• B. Hypophosphatemic rickets
• C. Type 1 VDDR
• D. Type 2 VDDR

Hint:

In cases of rickets with normal calcium and PTH, but low phosphate and high ALP, consider hypophosphatemic rickets. Phosphate deficiency is the hallmark.

Answer 1

The Correct Option is B

The biochemical analysis of this child presents with normal calcium (Ca2+), normal parathyroid hormone (PTH), reduced phosphate, and elevated alkaline phosphatase (ALP). This combination of findings is characteristic of hypophosphatemic rickets, a form of rickets where the primary problem is phosphate deficiency rather than calcium or vitamin D deficiency. - Nutritional rickets is typically caused by vitamin D deficiency, leading to low calcium levels, elevated PTH, and hypophosphatemia, but in this case, calcium and PTH levels are normal, which rules out nutritional rickets. - Type 1 VDDR (Vitamin D Dependent Rickets Type 1) is characterized by a defect in the enzyme 1-alpha-hydroxylase, which leads to low calcium and high PTH, which is not seen in this case. - Type 2 VDDR (Vitamin D Dependent Rickets Type 2) involves a defect in the vitamin D receptor, leading to low calcium, elevated PTH, and hypophosphatemia, which does not fit with the normal calcium and PTH levels seen here. In hypophosphatemic rickets, the primary issue is defective renal phosphate reabsorption, which results in low phosphate levels despite normal calcium and PTH levels. This condition leads to defective bone mineralization, which results in symptoms such as growth failure, skeletal deformities, and muscle weakness.