IMPE Abstracts

Introduction: Phaeochromocytomas and paragangliomas (PPGLs)are rare neuroendocrine tumors. The number of genetically determined PPGLs with specific variants rises to approximately 70%. The genetic status of patients with PPGLs is key for precision diagnosis, treatment and surveillance of affected patients and their families. Pathogenic gain-of-function variants in EPAS1gene, mainly as germline mosaicism or somatic mutations, cause its activation and lead to constitutive stability of HIF2A and upregulation of genes related to hypoxia, angiogenesis, and metabolism.

Patient and methods: A 9-year-old boy presented with vomiting, headache, dizziness, high blood pressure. Renal angiography was performed showing stenosis of the right renal artery and renal hypoplasia. An intercavoaortic tumor was visualized in imaging studies. Nephrectomy and partial resection of paravertebral tumor was performed. He continued in the postoperative with hypertension, tachycardia and sweating. He was admitted to our hospital to complete surgical treatment for a retroperitoneal tumor. It was completely resected. Diagnosis of paraganglioma was confirmed. DNA from peripheral blood was obtained from the patients and his mother. First, a candidate gene approach was used, not detecting any relevant variants in VHL, SDHD, and SDHB genes. Genomic diagnosis was performed by NGS (Clinical exome, TruSight One, NextSeq500llumina). NGS results were analyzed by own designed bioinformatic pipelines, and B platform (Bitgenia) was used to prioritize variants based on a virtual panel of candidate genes related to the clinical phenotype (HPO terms)of the patient. All variants found were classified according to ACMGcriteria.

Results: A novel heterozygous variant in EPAS1, NC_000002.11(NM_001430.5):c.2220G>A, NP_001421.2:p.(Met740Ile) was found in this patient. The variant was classified as VUS. Targeted exome NGS showed an average coverage of 72X, with ≥20X coverage in 94% of bases in the virtual gene panel. The variant, which predicts a change from Methionine to Isoleucine at position 740 of the protein, is absent in in all population frequency databases (GnomAD, ExAC, 1000 Genomes). The position was read with a depth of 75X, with the adenine at position 2220 in 33 reads, compatible with a heterozygous presentation. The variant was confirmed by Sanger sequencing in the patient and segregation analysis indicated that it was inherited from his mother.

Conclusion: The successful implementation of NGS allowed us to identify a novel variant in EPAS1 as a predisposing potential for paraganglioma in our patient. This result underscores the importance of performing genetic screening in children with pheochromocytoma/paraganglioma due to the high frequency of genetic mutations. Moreover, the diagnosis of this syndrome has clinical value since the identification of the pathways involved in pathogenesis may have potential therapeutic implications.