Differential Diagnosis for 59-year-old Male with HTN, Thyroid Disease, Bone Pain, Edema on MRI, and Elevated Calcium

Single Most Likely Diagnosis

• Hyperparathyroidism: Given the patient's history of thyroid disease, bone pain, edema on MRI, and a one-time finding of elevated calcium, hyperparathyroidism is a strong consideration. Hyperparathyroidism can lead to hypercalcemia, which in turn can cause bone pain due to osteitis fibrosa cystica, and edema due to hypercalcemia-induced renal impairment.

Other Likely Diagnoses

• Paget's Disease of Bone: This condition can cause bone pain and edema, and while it doesn't directly cause hypercalcemia, it can lead to elevated alkaline phosphatase levels, which might be seen in the context of CMP (Comprehensive Metabolic Panel). The patient's age and symptoms make this a plausible diagnosis.
• Metastatic Bone Disease: Given the patient's age, metastatic bone disease from a primary malignancy (e.g., prostate, breast, lung, or kidney cancer) could explain the bone pain and edema. Some cancers can also lead to hypercalcemia through the production of parathyroid hormone-related protein (PTHrP).
• Thyroid Hormone Excess (Hyperthyroidism): Although the patient has a history of thyroid disease, if not properly managed, hyperthyroidism could lead to bone pain due to accelerated bone turnover and potentially elevated calcium levels due to increased bone resorption.

Do Not Miss Diagnoses

• Multiple Myeloma: A plasma cell dyscrasia that can cause bone pain, edema (due to renal impairment), and hypercalcemia. It's crucial to consider this diagnosis due to its potential for significant morbidity and mortality if left untreated.
• Vitamin D Intoxication: Excessive intake of vitamin D can lead to hypercalcemia, which in turn can cause bone pain and edema. This condition is easily treatable but can be dangerous if not recognized.
• Malignancy-associated Hypercalcemia: Various malignancies can cause hypercalcemia through different mechanisms (e.g., PTHrP production, osteolytic metastases). Identifying and treating the underlying malignancy is critical.

Rare Diagnoses

• Familial Hypocalciuric Hypercalcemia (FHH): A rare genetic disorder that mimics primary hyperparathyroidism but is characterized by hypocalciuria. It's essential to distinguish FHH from hyperparathyroidism, as the former does not require surgical intervention.
• Sarcoidosis: A systemic granulomatous disease that can cause hypercalcemia due to increased vitamin D production by macrophages within granulomas. Bone pain and edema could be part of the clinical presentation, especially if there's skeletal involvement.

Best Workup

1. Repeat Calcium Level: To confirm hypercalcemia.
2. Parathyroid Hormone (PTH) Level: To differentiate between primary hyperparathyroidism and other causes of hypercalcemia.
3. Vitamin D Levels: To assess for vitamin D intoxication or deficiency.
4. Bone Markers (e.g., Alkaline Phosphatase, Osteocalcin): To evaluate bone turnover.
5. Imaging Studies (e.g., X-rays, Bone Scan): To assess for bone lesions or metastatic disease.
6. Serum and Urine Protein Electrophoresis (SPEP/UPEP): To rule out multiple myeloma.
7. Thyroid Function Tests: To evaluate the current status of thyroid disease.
8. MRI and Other Imaging: To further evaluate edema and bone pain, potentially guiding a biopsy if a focal lesion is identified.

This approach will help narrow down the differential diagnosis and guide further management based on the underlying cause of the patient's symptoms.