American Board of Internal Medicine (ABIM) Certification Practice Exam

Which syndrome is characterized by bone pain and hypophosphatemia along with low active vitamin D levels?

1. Bartter syndrome

2. Fanconi syndrome

3. Oncogenic osteomalacia

4. Acute tubular necrosis

The correct answer is: Oncogenic osteomalacia

Oncogenic osteomalacia is characterized by bone pain, hypophosphatemia, and low active vitamin D levels. This syndrome is often caused by tumors, typically in the mesenchymal tissues, which secrete substances that lead to phosphate wasting. The excessive loss of phosphate results in osteomalacia, characterized by softening of the bones due to poor mineralization. Patients with oncogenic osteomalacia often experience significant bone pain and may have fractures due to weakened bones, further emphasizing the pain component. The low levels of active vitamin D are a result of impaired absorption and metabolism of phosphates, leading to inadequate calcium absorption and mineralization of bone. The other mentioned syndromes do not typically present with this specific combination of symptoms. For instance, Bartter syndrome primarily involves electrolyte imbalances due to renal tubular dysfunction, but it does not present with hypophosphatemia and low active vitamin D as a main feature. Fanconi syndrome, while it can lead to phosphate wasting, is associated with a broader spectrum of metabolic derangements, including glucosuria and aminoaciduria, rather than the specific bone pain and vitamin D deficiency seen in oncogenic osteomalacia. Acute tubular necrosis can cause renal impairment but is not typically linked