MON-LB061 Cushing Syndrome Due to an Adrenocortical Carcinoma in a Baby with Atypical Beckwith-Wiedemann Syndrome

Introduction: Beckwith-Wiedemann syndrome (BWS) is a congenital tumor-predisposition syndrome of which around 70% develops because of the methylation defects in the imprinted genes at chromosome 11p15.5. KCNQ1OT1 hypomethylation is the most common underlying genetic aberration in sporadic BWS, accounting for 50% of the sporadic cases but confers the least tumor risk. Case: We present a 5 month-old girl who presented with an excessive weight gain, arrested growth in height and head circumference and Cushingoid face starting from two months of age. She was born following an in vitro fertilization (IVF) pregnancy to non-consanguineous parents with negative family history for malignancies. She had signs of Cushing syndrome, nevus flammeus between eyebrows, microcephaly, a palpable mass on upper right abdomen and Tanner stage 2 pubic hair on physical examination. She had elevated free cortisol and suppressed ACTH and dexamethasone suppression test was consistent with Cushing Syndrome. Abdominal MRI revealed a right adrenocortical mass measuring 4x3x1.5 cm. Histopathology confirmed a diagnosis of adrenocortical carcinoma. There was no adrenal cortex cytomegaly at histopathological evaluation. Methylation analysis of the imprinted domains at chromosome 11p15.5 revealed hypomethylation at KvDMR (KCNQ1OT1 gene). Except for a nevus flammeus and adrenocortical carcinoma, no other features of BWS were present. Growth rate of height and head circumference normalised after tumor resection. Conclusion: This case establishes that KCNQ1OT1 hypomethylation should not only be considered in cases with a clear BWS phenotype but in all pediatric cases of apparently sporadic adrenocortical carcinoma. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. Abstracts presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.