Question

On radiographic examination, a pediatric patient is found to have osteopenia and multiple fractures in various stages of healing. Serum laboratory results show: Calcium: low. Phosphorus: low. Creatinine: normal. Alkaline phosphatase: high. 25-OH vitamin D: Low. 1,25 (OH)2 vitamin D: Low. PTH: high. Which of the following is the most likely diagnosis?

1: Renal tubular acidosis
2: Osteogenesis imperfecta
3: Vitamin D deficiency rickets
4: Vitamin D dependent rickets type 2

Answer 1

The diagnosis for the case described with multiple fractures, low serum calcium and phosphorus, and high PTH is most likely vitamin D deficiency rickets (option 3). The low levels of vitamin D lead to impaired bone mineralization and subsequent bone deformities.

Step-by-step explanation:

The most likely diagnosis for the pediatric patient with osteopenia, multiple fractures in various stages of healing, low serum calcium and phosphorus, normal creatinine, high alkaline phosphatase, low 25-OH vitamin D, low 1,25 (OH)2 vitamin D, and high parathyroid hormone (PTH) is vitamin D deficiency rickets. This condition is characterized by defective mineralization of bone, leading to bone deformities and is most commonly due to a deficiency of vitamin D, which is essential for the intestinal absorption of calcium and phosphate.


The deficiency of vitamin D is the underlying cause of the low serum phosphorus and the defects in calcification of bones. Furthermore, the high PTH level is a response to low blood calcium levels, trying to compensate by increasing calcium reabsorption from the bones and the kidneys, thereby exacerbating the bone weakening.