Germline USP8 Mutation Associated With Pediatric Cushing Disease and Other Clinical Features: A New Syndrome.

Background: Somatic mutations in the ubiquitin-specific peptidase 8 (USP8) gene are common in corticotropinomas of children with Cushing disease (CD). We report a unique patient with a germline USP8 mutation who presented with CD and a constellation of other findings that constitute an intriguing genetic syndrome.

Case Description: We describe a 16-year-old female with CD, developmental delay, dysmorphic features, ichthyosiform hyperkeratosis, chronic lung disease, chronic kidney disease, hyperglycemia, dilated cardiomyopathy with congestive heart failure, and previous history of hyperinsulinism and partial GH deficiency. She was diagnosed with CD at 14 years old and underwent transsphenoidal surgery. Despite initial improvement, she developed recurrent CD.

Methods: DNA was extracted from peripheral blood and tumor DNA; whole-exome and Sanger confirmatory sequencing were performed. Immunohistochemistry was performed on the resected adenoma.

Results: A de novo germline heterozygous USP8 mutation (c.2155T>C, p.S719P) in the critical 14-3-3 binding motif hot spot locus of the gene was identified in both the peripheral blood and tumor DNA. Histopathologic evaluation of the resected tumor confirmed an ACTH-secreting adenoma.

Conclusion: Somatic USP8 mutations are common in adenomas causing CD, but to date, no germline defects have been reported. We describe a patient with a de novo germline USP8 mutation with recurrent CD and multiple other medical problems. This unique patient informs us of the multitude of signaling events that may be controlled by USP8.