Question
A 2-year-old child presents with bow legs, normal calcium, and high PTH. The probable diagnosis is?
| A. | Scurvy |
| B. | Rickets |
| C. |
Hyperparathyroidism |
| D. |
Diabetes Insipidus |
|
Correct Answer � B Explanation |
 |
Rickets is a disorder of defective mineralization of growing bones due to vitamin D deficiency, resulting in:
-
-
Growth plate widening
-
Bowing of weight-bearing long bones
-
Elevation of alkaline phosphatase
-
Elevated PTH due to secondary hyperparathyroidism
-
Normal or low calcium, low phosphate
-
Lab correlation:
-
Normal calcium: due to compensatory increase in PTH
-
Elevated PTH: reflects secondary hyperparathyroidism due to hypovitaminosis D
-
Supports the diagnosis of nutritional rickets
Why Other Options Are Incorrect:
A. Scurvy
-
Caused by vitamin C deficiency, leading to defective collagen synthesis.
-
Presents with bleeding gums, irritability, pseudoparalysis, and subperiosteal hemorrhages — not bow legs.
-
PTH levels are not elevated in scurvy.
C. Hyperparathyroidism
-
Usually seen in adults; primary hyperparathyroidism causes high calcium, not normal calcium.
-
It doesn’t cause bowing of legs in children.
D. Diabetes Insipidus
-
Involves ADH deficiency or resistance, leading to polyuria, polydipsia, and dehydration.
-
No relevance to bone deformity or elevated PTH.