sarcoidosis and electrolyte abnormality

 Q: 38 year old female with a history of sarcoidosis is admitted to ICU with mental status change after a week of hike in mountains. Which one electrolyte abnormality is expected?

Answer: Hypercalcemia

Hypercalcemia in sarcoidosis gets aggravated by sunlight. High serum calcitriol concentration increases intestinal calcium absorption. There is also a mild component of the calcitriol-induced increase in bone resorption. 

The full description of the pathophysiology of hypercalcemia in sarcoidosis is beyond the scope of  this website but it would be worthy of mentioning a relatively less described phenomenon of Parathyroid hormone-related protein (PTHrP). This protein is well described in the etiology of hypercalcemia in cancer patients but is also found in a majority of biopsies of granulomatous tissue from sarcoid patients.

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References:

1. Adams JS. Vitamin D metabolite-mediated hypercalcemia. Endocrinol Metab Clin North Am 1989; 18:765. 

2. Sharma OP. Vitamin D, calcium, and sarcoidosis. Chest 1996; 109:535.

3. Insogna KL, Dreyer BE, Mitnick M, et al. Enhanced production rate of 1,25-dihydroxyvitamin D in sarcoidosis. J Clin Endocrinol Metab 1988; 66:72. 

4. Zeimer HJ, Greenaway TM, Slavin J, et al. Parathyroid-hormone-related protein in sarcoidosis. Am J Pathol 1998; 152:17.