Differential Diagnosis for 74 y/o Female with Malaise, Cough, Fatigue, and Elevated Calcium

• Single Most Likely Diagnosis
  • Hyperparathyroidism: Given the patient's age, symptoms of malaise, fatigue, and elevated calcium levels, hyperparathyroidism is a strong consideration. It is a common cause of hypercalcemia, especially in older adults, and can be associated with a range of symptoms including fatigue and malaise.
• Other Likely Diagnoses
  • Pneumonia or other infections: The patient's cough and fatigue could suggest a respiratory infection. While the elevated calcium is not directly explained by this, infections can sometimes lead to hypercalcemia through various mechanisms, including the production of vitamin D-like substances by macrophages.
  • Malignancy (e.g., lung cancer, multiple myeloma): Both lung cancer and multiple myeloma can cause hypercalcemia through the production of parathyroid hormone-related protein (PTHrP) or by bone destruction, respectively. Given the patient's age and symptoms, malignancy is a consideration.
  • Vitamin D toxicity: Although less common, excessive intake of vitamin D supplements can lead to hypercalcemia. This could be particularly relevant in a patient with hypothyroidism who might be taking supplements.
• Do Not Miss Diagnoses
  • Hypercalcemia of malignancy with an occult primary: It's crucial not to miss a malignancy, especially one that could be treated if caught early. The presence of hypercalcemia can sometimes be the first sign of an underlying cancer.
  • Sarcoidosis: This condition can cause hypercalcemia due to increased vitamin D production by macrophages in granulomas. Sarcoidosis can present with nonspecific symptoms such as malaise and fatigue, and it's a diagnosis that could significantly alter management.
• Rare Diagnoses
  • Familial hypocalciuric hypercalcemia (FHH): A rare genetic disorder that leads to hypercalcemia due to altered calcium sensing by the parathyroid glands. It's less likely given the patient's age at presentation but could be considered if other causes are ruled out.
  • Lymphoma: Certain types of lymphoma can cause hypercalcemia, either through direct bone involvement or the production of cytokines that stimulate osteoclast activity. While less common, lymphoma is a diagnosis that would significantly impact treatment and prognosis.