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 case involves a child presenting with growth failure and specific biochemical findings: normal calcium (Ca²⁺), normal parathyroid hormone (PTH), reduced phosphate levels, and increased alkaline phosphatase (ALP). To diagnose, we analyze these results:

• Normal Ca²⁺ and PTH: Indicates that calcium regulation is not affected, often ruling out conditions related to calcium metabolism abnormalities.
• Reduced Phosphate: Suggests a phosphate handling issue, as phosphate is crucial for bone mineralization.
• Increased ALP: Often indicates increased bone turnover or growth, commonly seen in rickets and osteomalacia related to defective bone mineralization.

The key points here are normal PTH and Ca²⁺, combined with low phosphate levels. These findings suggest a form of rickets not related to vitamin D deficiency, particularly when vitamin D levels are not accounted for indicating a different etiology.

Identifying Hypophosphatemic Rickets: This condition is characterized by genetic causes leading to phosphate wasting at the kidney level, resulting in hypophosphatemia (low serum phosphate). It is not related to vitamin D deficiency or insufficiency, thus ruling out nutritional rickets, Type 1 VDDR (Vitamin D Dependent Rickets Type 1), and Type 2 VDDR.

Given the biochemical profile:

• Growth failure
• Normal Ca²⁺
• Normal PTH
• Reduced phosphate
• Increased ALP

The diagnosis of Hypophosphatemic Rickets is confirmed, as it aligns with all presented findings.