Differential Diagnosis for Elevated Calcium Levels in a Vegan Patient

• Single Most Likely Diagnosis
  • Primary hyperparathyroidism: This condition is characterized by an overproduction of parathyroid hormone (PTH), leading to elevated calcium levels. It is a common cause of hypercalcemia and can occur in anyone, regardless of diet.
• Other Likely Diagnoses
  • Vitamin D toxicity: Although the patient is vegan, they may still be taking vitamin D supplements, which can cause elevated calcium levels if taken in excess.
  • Familial hypocalciuric hypercalcemia (FHH): This is a genetic disorder that affects calcium regulation and can cause elevated calcium levels.
  • Hypercalcemia of malignancy: Certain types of cancer, such as lung, breast, and kidney cancer, can produce substances that stimulate the release of calcium from bones, leading to elevated levels.
• Do Not Miss Diagnoses
  • Hyperparathyroidism due to lithium use: Lithium can cause hyperparathyroidism, leading to elevated calcium levels. Although the patient's vegan diet is mentioned, their medication history is not, making this a crucial diagnosis not to miss.
  • Multiple myeloma: This type of blood cancer can cause hypercalcemia due to bone destruction and release of calcium into the bloodstream.
  • Vitamin A toxicity: Excessive intake of vitamin A can cause hypercalcemia, and although less common, it is a potentially life-threatening condition that should not be missed.
• Rare Diagnoses
  • Sarcoidosis: This autoimmune disorder can cause hypercalcemia due to increased vitamin D production.
  • Thyrotoxicosis: Excessive thyroid hormone production can lead to hypercalcemia, although this is a rare cause.
  • Pheochromocytoma: A rare tumor of the adrenal gland that can produce substances leading to hypercalcemia.
  • Williams syndrome: A genetic disorder that can cause hypercalcemia due to abnormal calcium regulation.