Pseudohyperkalemia due to cryohydrocytosis in GLUT1 deficiency syndrome. A case report and literature review.

Cryohydrocytosis is a form of stomatocytosis characterized by the leakage of sodium and potassium from red blood cells at low temperatures, characterized by pseudohyperkalemia. Stomatin-deficient cryohydrocytosis is an extremely rare variant that only recently has been related to pathogenic variants in the SLC2A1 gene, encoding the main glucose transporter of the blood-brain-barrier and red blood cells, GLUT1. It follows that GLUT1 deficiency syndrome, a rare but significant cause of metabolic epilepsy, may present with stomatin-deficient cryohydrocytosis, although this correlation has only been reported in a few instances. We present the case of a patient carrying a de novo SLC2A1 pathogenic variant presenting with GLUT1 deficiency syndrome, pseudohyperkalemia, and splenomegaly consistent with cryohydrocytosis. The mutation has never been described. We also review the previously reported cases of stomatin-deficient cryohydrocytosis in the literature. As highlighted by our case, elevated potassium levels are a cause of concern, and GLUT1 deficiency syndrome patients are thus at risk of being subjected to unnecessary examinations; pseudohyperkalemia may be underrecognized in clinical practice.