Persistent Hypomagnesemia in the Context of Refeeding and Supplementation: A Case Report.

Refeeding syndrome is characterized by electrolyte imbalances that occur during nutritional replenishment in malnourished patients. Hypomagnesemia is a potential complication.  We present a unique case of a female, young adult patient with anorexia nervosa who experienced persistent hypomagnesemia during inpatient refeeding that did not resolve with magnesium supplementation. Extended diagnostic evaluation included genetic testing that revealed heterozygous variants of uncertain significance in the PKD1 and SCNN1G genes as well as a pathogenic variant in the SMARCAL1 gene. These variants are not currently associated with a known renal disorder.  While the extensive work-up for persistent hypomagnesemia in the context of appropriate supplementation did not yield a definitive diagnosis, this case emphasizes the need to pursue alternative etiologies and treatments of unexpectedly refractory electrolyte abnormalities during the course of refeeding.