ODP267 Doege-Potter Syndrome in a Patient With Mediastinal Solitary Fibrous Tumor
Authors: Mon Zin Myet , Mokshagundam Sriprakash , Cunningham Jonathan 
Published: November 2022

Abstract
N on-islet cell tumor hypoglycemia (NICTH) is a rare paraneoplastic syndromethat presents mostly with hypoinsulinemic hypoglycemia and is associated with benign and malignant neoplasms other than insulinoma. Doege-Potter Syndrome (DPS) is characterized when NICTH is secondary to a solitary fibrous tumor (SFT). The following is a case of DPS in which the patient presented with refractory hypoglycemia. An 81-year-old Caucasian male presented to emergency department with a 10-day history of worseningneuroglycopenic symptoms in fasting state. He experienced worsening night sweats, unsteadiness while walking, dizziness, and irritation, which resolved after breakfast each morning. Five years prior to this admission, he was diagnosed with a malignant mediastinal SFT (atypical spindle cell neoplasm). He was treated with radiation followed by mass resection (9.5×6.5×7.9 cm). Despite treatment with 3 lines of therapy of phase 1 clinical trial, his disease continued to progress with a right paraspinal mass and bilateral lung metastases being subsequently found. In ED, his initial blood glucose was 53 mg/dL. Despite receiving IV dextrose pushes and a continual dextrose infusion, he continued to be hypoglycemic. Upon admission, blood work revealed blood glucose of 41 mg/dL, low insulin level of 0.4 uIU/mL (2.6-24.9 uIU/mL) and low C-peptide level of 0.9 ng/mL (1.1-4.4ng/mL). Proinsulin (4.4pmol/L), Cortisol (17.2mcg/dL) and A1c (5.2%) were all within normal limits. Serum and urine ketones as well as a blood sulfonylurea panel were negative. He was started on hydrocortisone 50 mg 8 hourly for insulin-independent hypoglycemia. His IGF1 level was 46 ng/mL (55-166ng/mL), and IGF2 level was 564 ng/mL (333-967ng/mL) with a high IGF2: IGF1 ratio of 12. He was discharged home with same hydrocortisone regimen. On follow-up, hydrocortisone dose was reduced to 30-30-20 mg. He passed away 4 months later after being hospitalized for hypoxic respiratory failure secondary to a pleural effusion. Interestingly, he was maintained on the same regimen of hydrocortisone up until his death and did not have recurrence of severe hypoglycemic episodes. The main mechanism of NICTH is tumoral overexpression of the IGF2 gene and aberrant post-translational processing, resulting in partially processed high-molecular-weight IGF2 (big-IGF2). Big- IGF2 has a lower affinity for IGF-binding proteins, which favors its own availability to IGF1 and insulin related receptors resulting in profound hypoglycemia and occasionally acromegaloid features. Diagnosis of NICTH is typically made byan IGF2: IGF1 ratio of greater than 10 (normal 3: 1)due to unavailability of commercial assays for big-IGF2. Radical tumor resection is the definitive treatment of NICTH. In unresectable neoplasms, tumor debulking, or medical therapies such as glucocorticoids, recombinant GH, and glucagon are used to alleviate hypoglycemic symptoms. Exploring more about effectiveness of chemotherapy regimens in controlling NICTH will be helpful in inoperable tumors.
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