A comprehensive next generation sequencing-based genetic testing strategy to improve diagnosis of inherited pheochromocytoma and paraganglioma.

CONTEXT: Pheochromocytomas and paragangliomas are notable for a high frequency of inherited cases, many of which present as apparently sporadic tumors. OBJECTIVE: The objective of this study was to establish a comprehensive next generation sequencing (NGS)-based strategy for the diagnosis of patients with pheochromocytoma and paraganglioma by testing simultaneously for mutations in MAX, RET, SDHA, SDHB, SDHC, SDHD, SDHAF2, TMEM127, and VHL. DESIGN: After the methodology for the assay was designed and established, it was validated on DNA samples with known genotype and then patients were studied prospectively. SETTING: The study was performed in a diagnostic genetics laboratory. PATIENTS: DNA samples from 205 individuals affected with adrenal or extraadrenal pheochromocytoma/head and neck paraganglioma (PPGL/HNPGL) were analyzed. A proof-of-principle study was performed using 85 samples known to contain a variant in 1 or more of the genes to be tested, followed by prospective analysis of an additional 120 samples. MAIN OUTCOME MEASURES: We assessed the ability to use an NGS-based method to perform comprehensive analysis of genes implicated in inherited PPGL/HNPGL. RESULTS: The proof-of-principle study showed that the NGS assay and analysis gave a sensitivity of 98.7%. A pathogenic mutation was identified in 16.6% of the prospective analysis cohort of 120 patients. CONCLUSIONS: A comprehensive NGS-based strategy for the analysis of genes associated with predisposition to PPGL and HNPGL was established, validated, and introduced into diagnostic service. The new assay provides simultaneous analysis of 9 genes and allows more rapid and cost-effective mutation detection than the previously used conventional Sanger sequencing-based methodology.

Polymorphisms in ABCB11 and ATP8B1 Associated with Development of Severe Intrahepatic Cholestasis in Hodgkin's Lymphoma.

We report a young man presenting with jaundice and severe debilitating intrahepatic cholestasis 7 months before the diagnosis of Hodgkin's lymphoma. Serum gamma-glutamyl transferase (GGT) activity was not raised. Liver biopsy demonstrated deficiency of canalicular GGT and bile salt export pump expression, which suggested "benign" recurrent intrahepatic cholestasis. Direct sequencing of genomic DNA was therefore undertaken to look for mutations in ATP8B1 and ABCB11. Cholestasis and pruritus are well recognized presenting features of Hodgkin's lymphoma. However, striking in this case is that the intrahepatic cholestasis presented and resolved 7 months before the diagnosis. Furthermore, 4 polymorphisms were identified in ATP8B1 in this patient-c.696T > C (rs319438), c.811A > C (rs319438), c.2855G > A (rs1296811) and c.3454G > A (rs222581)-and two polymorphisms in ABCB11-c.1331T > C (rs2287622) and c.3084A > G (rs497692); 2 of which have been associated with intrahepatic cholestasis of pregnancy. We therefore postulate that these polymorphisms predisposed this patient to the development of intrahepatic cholestasis within the abnormal pro-inflammatory cytokine milieu typical for Hodgkin's lymphoma. This case shows for the first time that some polymorphisms in ABCB11 and ATP8B1 may predispose to the development of intrahepatic cholestasis in Hodgkin's lymphoma. It also demonstrates the importance of close clinical surveillance for the development of Hodgkin's lymphoma in patients presenting with unexplained intrahepatic cholestasis.

Investigation of the Birt-Hogg-Dube tumour suppressor gene (FLCN) in familial and sporadic colorectal cancer.

BACKGROUND Birt-Hogg-Dubé (BHD) syndrome is an autosomal dominant multisystem disorder with skin (fibrofolliculomas or trichodiscomas), lung (cysts and pneumothorax) and kidney (renal cell carcinoma) tumours. Although colorectal neoplasia was reported initially to be part of the BHD phenotype, some recent studies have not confirmed this association. METHODS A series of clinical and laboratory studies was undertaken to investigate possible relationships between colorectal neoplasia and the BHD gene (FLCN). The studies investigated whether individuals with familial colorectal cancer of unknown cause might have unsuspected germline FLCN mutations, looked for somatic FLCN C(8) tract mutations in microsatellite unstable sporadic colorectal cancers, and assessed the risk of colorectal neoplasia and possible genotype-phenotype correlations in BHD patients. RESULTS Although it was found previously that germline FLCN mutations can be detected in approximately 5% of patients with familial renal cell carcinoma, germline FLCN mutations were not detected in 50 patients with familial non-syndromic colorectal cancer. Analysis of genotype-phenotype correlations for two recurrent FLCN mutations identified in a subset of 51 families with BHD demonstrated a significantly higher risk of colorectal neoplasia in c.1285dupC mutation (within the exon 11 C(8) mononucleotide tract) carriers than in c.610delGCinsTA mutation carriers (chi(2)=5.78, p=0.016). Somatic frameshift mutations in the FLCN exon 11 C(8) mononucleotide tract were detected in 23% of sporadic colorectal cancers with microsatellite instability, suggesting that FLCN inactivation might contribute to colorectal tumourigenesis. CONCLUSIONS These findings suggest that the previously reported clinical heterogeneity for colorectal neoplasia may reflect allelic heterogeneity and the risk of colorectal neoplasia in BHD syndrome requires further investigation.