SUN-186 - A Case of Delayed-Onset Severe Persistent Hypercalcemia and Subcutaneous Fat Necrosis in an Infant

Background:
Subcutaneous fat necrosis (SCFN) is a rare, self-limited panniculitis seen in term neonates, typically associated with perinatal stress, hypoxia, or therapeutic hypothermia. Although the cutaneous lesions resolve spontaneously, associated hypercalcemia may become severe and lead to nephrocalcinosis, cardiac arrhythmia, or neurological complications. Hypercalcemia is usually a delayed finding, emerging during resolution of skin lesions.

Methods:
Case report of a patient with a delayed-onset, severe, persistent episode of SCFN.

Case Presentation:
A 27-day-old male presented with failure to thrive and subcutaneous nodules on his back. He was born large for gestational age at 41 weeks, via emergency cesarean section for failed induction and non-reassuring fetal heart tracing, requiring resuscitation at birth. He was admitted to the NICU for respiratory distress and transient multi-organ dysfunction. At NICU discharge on DOL 10, serum calcium (Ca) was 11 mg/dL (8.5-10.5 mg/dL).

At presentation to ED at DOL 27, serum Ca was 23.6 mg/dL, phosphorus was 3.6 mg/dL (4.9-7.5 mg/dL), and magnesium was 2.1 mg/dL (1.5-2.5 mg/dL). PTH was suppressed ( < 6.3 pg/mL (10-65 pg/mL)), 25-hydroxyvitamin D was low (15.8 ng/mL (30-89 ng/mL)), and 1,25-hydroxyvitamin D was mildly elevated 207 pg/mL (44.3–212.9 pg/mL). Initial EKG with ST elevations was consistent with hypercalcemic changes. On physical exam, he had diffuse, erythematous, firm lumpy lesions on his back. Dermatologic ultrasound confirmed SCFN, and renal-bladder ultrasound revealed bilateral medullary nephrocalcinosis. Despite aggressive treatment with IV hydration, furosemide and hydrocortisone, Ca remained elevated (21.4 mg/dL) and required multiple doses of pamidronate (0.25 mg/kg) and calcitonin (4-6u/kg), as well as low-calcium formula, for Ca to improve to 11.9 mg/dL on day 5 of admission. EKG changes resolved. During the hospitalization, the nodules on his back softened and decreased in size; however, on Day 19 of admission, new nodules were noted on his arms, thighs, and face. Rebound hypercalcemia (14.1 mg/dL) occurred, requiring another dose of pamidronate (0.5 mg/kg). His Ca level improved to 9.6 mg/dL, and he was discharged on Day 26 of admission (DOL 53).

Conclusion:
This case highlights a unique course of SCFN-associated hypercalcemia, which was both delayed in onset and prolonged in course. Neonates with SCFN should be screened for hypercalcemia at diagnosis and followed longitudinally, even if initial calcium level is normal. Early bisphosphonate therapy, in conjunction with calcitonin, can be important to prevent serious sequelae in refractory or severe hypercalcemia.

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