SUN-616 Phosphomannomutase 2 (PMM2)-Congenital Disorder of Glycosylation in a Patient with Dandy Walker Malformation

Abstract Disclosure: M. Kazim: None. S.S. Krishnasamy: None. Background: (PMM2)-congenital disorder of glycosylation (CDG) is a disorder of protein N-glycosylation characterized by deficiency/dysfunction of PMM2. We present a case of a patient with Dandy Walker Malformation (DWM) presenting with severe persistent hypoglycemia. Clinical Case: We were consulted on 24 y old African American female known case of DWM, congenital bilateral hearing loss, epilepsy, cerebral palsy, primary ovarian failure and, venous thromboembolism (VTE) for evaluation of persistent hypoglycemia. At birth she was in the NICU for hypoglycemia however since then she did not have any documented symptomatic hypoglycemia. Patient now presented with hypoglycemic symptoms after recent hospitalization for VTE and renal infarct. Labs showed ACTH 7 pg/mL, AM cortisol 10.2 mcg/dL, glucose 50mg/dl, C-peptide of 1.97 ng/ml, proinsulin 47 pmol/L, insulin 18.1 uIU/ml, Prolactin 10.4 ng/ml, TSH 1.71 mIU/L, Free T4 1.1 ng/dL, IGF-1 343 ng/mL, FSH 160 mIU/mL, LH 63.2 mIU/mL. CT abdomen and pelvis showed no pathology of the pancreas. Patient was hospitalized with severe hypoglycemia not responding to D10 infusion. Given hyper insulinemic hypoglycemia resistant to intravenous dextrose we initiated diazoxide 3 mg/kg q8h. she was also started on glucocorticoids for suspicion of autoimmune etiology of hypoglycemia. She responded quite well with improving blood sugars. She was referred to genetics given no clear cause of hypoglycemia established. Carbohydrate deficient transferrin test showed increased Mono-Oligo/Di-Oligo ratio of 0.32 (normal <0.06) and A-Oligo/Di-Oligo Ratio of 0.123 (normal <0.011). Patient is now on a stable regimen with diazoxide 100mg by mouth every 6 hours and high protein/complex carbohydrate diet with improvement of hypoglycemia. Conclusion: CDG are a wide spectrum of disorders associated with dysfunction of multiple organs particularly the brain and endocrine system. Cerebellar atrophy has been reported in 95.4% of cases with PMM2- CGD with the most common cerebellar symptom in patients being ataxia (1). To our knowledge only one other case has been published with PMM2- CDG and Dandy Walker Malformation (DWM). Due to paucity of cases involving CDG and DWM it is unclear if DWM is a separate entity in these patients or caused by CDG itself. CDG should be considered as a differential in patients with DWM presenting with hypoglycemia even in later aspect of life. Reference: (1)Altassan R, Péanne R, Jaeken J, et al. International clinical guidelines for the management of phosphomannomutase 2-congenital disorders of glycosylation: Diagnosis, treatment and follow up [published correction appears in J Inherit Metab Dis. 2019 May;42(3):577. doi: 10.1002/jimd.12082]. J Inherit Metab Dis. 2019;42(1):5-28. doi:10.1002/jimd.12024 Presentation: Sunday, July 13, 2025