CONTEXT: Germline loss-of-function CDKN1B gene variants cause the autosomal dominant syndrome of multiple endocrine neoplasia type 4 (MEN4). Even though pituitary neuroendocrine tumors are a well-known component of the syndrome, only 2 cases of Cushing's disease (CD) have so far been described in this setting. AIM: To screen a large cohort of CD patients for CDKN1B gene defects and to determine their functional effects. PATIENTS: We screened 211 CD patients (94.3% pediatric) by germline whole-exome sequencing (WES) only (n = 157), germline and tumor WES (n = 27), Sanger sequencing (n = 6), and/or germline copy number variant (CNV) analysis (n = 194). Sixty cases were previously unpublished. Variant segregation was investigated in the patients' families, and putative pathogenic variants were functionally characterized. RESULTS: Five variants of interest were found in 1 patient each: 1 truncating (p.Q107Rfs*12) and 4 nontruncating variants, including 3 missense changes affecting the CDKN1B protein scatter domain (p.I119T, p.E126Q, and p.D136G) and one 5' untranslated region (UTR) deletion (c.-29_-26delAGAG). No CNVs were found. All cases presented early (10.5 ± 1.3 years) and apparently sporadically. Aside from colon adenocarcinoma in 1 carrier, no additional neoplasms were detected in the probands or their families. In vitro assays demonstrated protein instability and disruption of the scatter domain of CDKN1B for all variants tested. CONCLUSIONS: Five patients with CD and germline CDKN1B variants of uncertain significance (n = 2) or pathogenic/likely pathogenic (n = 3) were identified, accounting for 2.6% of the patients screened. Our finding that germline CDKN1B loss-of-function may present as apparently sporadic, isolated pediatric CD has important implications for clinical screening and genetic counselling.

College of Medicine Sulaimani University Sulaimani Kurdistan Iraq

Department of Endocrinology Cochin Hospital Assistance Publique Hôpitaux de Paris Institut Cochin INSERM U1016 CNRS 8104 Paris Descartes University Paris France

Department of Laboratory Medicine and Pathology University of Minnesota Medical School Minneapolis Minnesota

Department of Pediatrics 2nd Faculty of Medicine Charles University and University Hospital Motol Prague Czech Republic

Epidemiology Branch Division of Intramural Population Health Research Eunice Kennedy Shriver National Institute of Child Health and Human Development Bethesda Maryland

Neurosurgery Unit for Pituitary and Inheritable Diseases National Institute of Neurological Disorders and Stroke Bethesda Maryland

Newborn Screening Program Wadsworth Center New York State Department of Health Albany New York

Section on Endocrinology and Genetics Eunice Kennedy Shriver National Institute of Child Health and Human Development Bethesda Maryland

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