Review Question - QID 109005

This patient is presenting with radiography significant for skeletal pathology suggestive of vitamin D deficiency (rickets). Patients with vitamin D deficiency will have a decreased calcium, phosphorus, and cholecalciferol and an increased alkaline phosphatase and PTH.

Patients with vitamin D deficiency can present with genu varum (Illustration A) and rachitic rosary (Figure A) from decreased mineralization of bone. Other symptoms of rickets include craniotabes, and frontal bossing. Vitamin D is converted to its active form by 25-hydroxylase in the liver and 1-alpha-hydroxylase in the kidney. Active vitamin D is involved in calcium absorption, phosphate absorption, and bone mineralization. When vitamin D is deficient, calcium and phosphorus levels will be low. The low serum calcium will trigger the parathyroid glands to release more PTH thus PTH levels are high, and the high PTH levels will result in an elevated alkaline phosphatase level. Treatment for these patients is vitamin D replacement.

Figure A demonstrates a rachitic rosary on chest radiograph. Figure B is a table that demonstrates the hormone and electrolyte changes that occur with vitamin D deficiency. Illustration A is a radiograph demonstrating genu varum - a common finding in vitamin D deficiency.

Incorrect Answers:
Answer 2: Low calcium, low phosphorus, low alkaline phosphatase, high PTH, and high cholecalciferol does not reflect the elevated alkaline phosphatase in rickets patients or the low vitamin D level.

Answer 3: High calcium, low phosphorus, high alkaline phosphatase, high PTH, and low cholecalciferol reflects primary hyperparathyroidism. Elevated PTH levels lead to increased calcium as well as phosphate wasting. Elevated PTH levels are also associated with elevated alkaline phosphatase levels.

Answer 4: High calcium, high phosphorus, high alkaline phosphatase, low PTH, and high cholecalciferol reflects vitamin D intoxication. High levels of vitamin D will lead to increased absorption of calcium and phosphate. The high serum calcium will suppress PTH release. The alkaline phosphatase level in this condition could be elevated, normal, or low.

Answer 5: Low calcium, low phosphorus, low alkaline phosphatase, high PTH, and low cholecalciferol could reflect secondary hyperparathyroidism where the elevated PTH is secondary to the decreased serum calcium.

Bullet Summary:
Vitamin D deficiency will demonstrate a decreased serum calcium, phosphorus, and cholecalciferol and an increased alkaline phosphatase and PTH.