Pseudohyperkalemia as a New Insight Into the Causes of Hyperkalemia Associated With Atopic Dermatitis.

Pseudohyperkalemia is defined as a falsely elevated serum potassium level caused by the release of potassium from blood cells during the clotting process, which occurs in vitro. Although hyperkalemia, a potentially life-threatening condition, has been associated with severe atopic dermatitis (AD) through mechanisms such as the 'aldosterone paradox,' pseudohyperkalemia has not been documented in AD. We present a case of pseudohyperkalemia in a nine-month-old girl with thrombocytosis associated with severe AD. Despite a serum potassium level of 7.3 mEq/L, the whole-blood potassium measured using a blood gas analyzer was 4.8 mEq/L. Therefore, we diagnosed the case as pseudohyperkalemia and decided not to treat the serum hyperkalemia. Following treatment with topical steroids and a Janus kinase inhibitor, the pseudohyperkalemia resolved as the skin condition improved and the platelet count decreased.