Hypercalcemia, hyperkalemia and supraventricular tachycardia in a patient with subcutaneous fat necrosis

Subcutaneous fat necrosis (SCFN) is a rare, self-limiting condition that has been associated with several complications including hypercalcemia. We present the case of a 6-week-old male who presented to his pediatrician with a dime-sized erythematous nodule consistent with SCFN, who was also found to have supraventricular tachycardia (SVT). Laboratory findings revealed hypercalcemia and hyperkalemia. Extensive evaluation for the electrolyte disturbances revealed no other etiology. This case reinforces that SCFN should be considered in newborns with hypercalcemia of unknown etiology. Additionally, this case is the first to suggest a connection between SCFN and hyperkalemia. Electrolyte abnormalities can potentially contribute to arrhythmogenesis and may have triggered the arrhythmia in our patient. Our case highlights the importance of remaining vigilant in the workup of atypical rashes of the infant, which should include early assessment of serum electrolytes.