Question

A child with this deformity. He has recurrent tooth abscesses. Calcium normal, Phosphorus low, PTH normal, ALP high. Diagnosis is?

• A. Nutritional rickets
• B. VDDR1 (Vitamin D Dependent Rickets Type 1)
• C. VDDR2 (Vitamin D Dependent Rickets Type 2)
• D. Hypophosphatemic rickets

Hint:

Nutritional rickets presents with normal calcium levels, low phosphorus, and elevated alkaline phosphatase, often due to vitamin D deficiency.

Answer 1

The Correct Option is A

A child presents with a deformity and recurrent tooth abscesses. The laboratory findings are calcium normal, phosphorus low, parathyroid hormone (PTH) normal, and alkaline phosphatase (ALP) high. These clues are essential to diagnose the condition.

The laboratory values and clinical symptoms suggest a form of rickets, characterized by defective mineralization or calcification of bones before epiphyseal closure. Let's evaluate each option based on these details:

• Nutritional rickets: Characterized by deficient mineralization of bones usually due to vitamin D deficiency. It results in low calcium and phosphorus levels, normal to high PTH, and elevated ALP. However, early states might show normal calcium if compensatory mechanisms have been operating, making phosphorus low and ALP high consistent with this case.
• VDDR1 (Vitamin D Dependent Rickets Type 1): Caused by defective renal conversion of 25(OH)D to 1,25(OH)₂D. This usually results in low calcium and phosphorus with elevated PTH, inconsistent with normal PTH here.
• VDDR2 (Vitamin D Dependent Rickets Type 2): This involves end-organ resistance to 1,25(OH)₂D (active vitamin D), leading to low calcium and low phosphorus with increased PTH. Again, normal PTH here rules out this option.
• Hypophosphatemic rickets: Caused by low phosphorus reabsorption in kidneys, shows normal calcium, low phosphorus, and normal PTH but does not typically present with high ALP in isolation. Recurrent dental issues also conform but are more specific to nutritional rickets.

The normal calcium and PTH with low phosphorus and elevated ALP best match nutritional rickets. Therefore, considering the symptoms and lab values, the diagnosis is Nutritional rickets.