Today we discussed an interesting case of acute encephalopathy due to hypercalcemia of malignancy due to bone metastases.

We first reviewed the importance of maintaining a broad differential for acute encephalopathy/delirium/acute confusional state/AMS.

We reviewed the following framework:

Neurologic / Toxic / Metabolic / Infectious / Other.

We then reviewed the differential for hypercalcemia. For those of you interested, please check out this awesome review video by Dr. Strong:

Our patient had hypercalcemia of malignancy and the following patients were made:

• It is the most common cause of hypercalcemia in inpatients
• The most commonly associated malignancies are breast, lung, multiple myeloma, and renal
• There are three major mechanisms for hypercalcemia of malignancy
  • Secretion of PTHrP – 80% of malignancy related hyperCa
  • Osteolytic Metastases – ~20% of cases
  • Increased 1,25-OH-Vitamin D (calcitriol) 2/2 to increased 1-alpha-hydroxylase activity from activated macrophages in lymphomatous (and also granulomatous) tissue
• We reviewed the PTH-based algorithm and determined that it was a PTH-independent process (PTH low or low-normal) and then used the PTHrP, calcidiol and calcitriol to guide to the correct diagnosis which was confirmed by MRI and bone scan

Finally, here is a way to distinguish between malignancy related hypercalcemia and primary hyperparathyroidism (most common cause in outpatients & higher co-occurrence in patients with malignancy)

For treatment options, please see the following blog post for more details!

https://scvmcmed.com/2019/03/26/hypercalcemia-of-malignancy/