Efficacy of Oral Furosemide Test for Primary Aldosteronism Diagnosis

Context

Confirmatory tests represent a fundamental step in primary aldosteronism (PA) diagnosis, but they are laborious and often require a hospital environment due to the risks involved.

Objective

To evaluate the efficacy of oral furosemide as a new confirmatory test for PA diagnosis.

Methods

We prospectively evaluated the diagnostic performance of 80 mg of oral furosemide in 64 patients with PA and 22 with primary hypertension (controls). Direct renin concentration (DRC) was measured before, and 2 hours and 3 hours after the oral furosemide. In addition, the oral furosemide test was compared with 2 other confirmatory tests: the furosemide upright test (FUT) and saline infusion test (SIT) or captopril challenge test (CCT) in all patients with PA.

Results

The cut-off of 7.6 µU/mL for DRC at 2 hours after oral furosemide had a sensitivity of 92%, specificity of 82%, and accuracy of 90% for PA diagnosis. In 5 out of 6 controls with low-renin hypertension, which might represent a PA spectrum, renin remained suppressed. Excluding these 6 controls with low-renin hypertension, the DRC cut-off of 10 µU/mL at 2 hours after oral furosemide had a sensitivity of 95.3%, specificity of 93.7% and accuracy of 95% for PA diagnosis. DRC after 3 hours of oral furosemide did not improve diagnostic performance. Using the cut-off of 10 µU/mL, the oral furosemide test and the FUT were concordant in 62 out of 64 (97%) patients with PA. Only 4 out of 64 cases with PA (6.4%) ended the oral furosemide test with potassium <3.5 mEq/L. Hypotension was not evidenced in any patient with PA during the test.

Conclusion

The oral furosemide test was safe, well-tolerated and represents an effective strategy for PA investigation.

Three Cases of Carney-Stratakis Syndrome: A Genetically Heterogeneous Disease

Carney-Stratakis syndrome (CSS) is an autosomal dominant rare syndrome, with incomplete penetrance, characterized by the association of paragangliomas and/or pheochromocytomas and gastrointestinal stromal tumors (GISTs). CSS is caused by germline heterozygous loss-of-function pathogenic variants (PVs) in the succinate dehydrogenase subunit genes (SDHB, SDHC, SDHD), with SDHB and SDHD being the most frequent. To date, only 2 germline SDHC PVs (c.43 C > T; c.405 + 1G > A) have been described in 3 patients with CSS. Three patients with CSS and very distinct clinical presentations are reported here: 1 caused by a germline SDHC large deletion and the others with metastatic GIST and negative genetic investigation for SDHx defects. Two cases (1 and 2) presented with pheochromocytoma (case 1 also with abdominal paraganglioma) and metastatic GIST. Although these 2 cases fulfilled the diagnostic criteria for CSS, the genetic investigation for SDHx PVs by next-generation sequencing and multiplex ligation-dependent probe amplification was negative. Case 3 had a large abdominal paraganglioma and a small low-grade GIST not associated with recurrence or metastasis. This case harbored a germline SDHC exon 3 deletion, not previously reported. In conclusion, CSS is a rare and morbid disease with distinct clinical presentations and genetic heterogeneity, which can contribute to underdiagnosis.

Evidence for a Founder Effect of SDHB Exon 1 Deletion in Brazilian Patients with Paraganglioma

BACKGROUND

Limited information is available concerning the genetic spectrum of pheochromocytomas and paragangliomas (PPGL) patients in South America. Germline SDHB large deletions are very rare worldwide, but most of the individuals harboring the SDHB exon 1 deletion were originated from the Iberian Peninsula. Our aim was to investigate the spectrum of SDHB genetic defects in a large cohort of Brazilian patients with PPGLs.

METHODS

The genetic investigation of 155 index PPGL patients was performed by Sanger DNA sequencing, multiplex ligation-dependent probe amplification, and/or target next-generation sequencing panel. Common ancestrality was investigated by microsatellite genotyping with haplotype reconstruction, and analysis of deletion breakpoint.

RESULTS

Among 155 index patients, heterozygous germline SDHB pathogenic or likely pathogenic variants (PV/LPVs) were identified in 22 cases (14.2%). Interestingly, the heterozygous SDHB exon 1 complete deletion was the most frequent genetic defect in SDHB, being identified in 8 out of 22 (36%) of the patients. Haplotype analysis of 5 SDHB flanking microsatellite markers demonstrated a significant difference in haplotype frequencies in a case-control permutation test (p = 0.03). More precisely, 3 closer/informative microsatellites were shared by 6 out of 8 apparently unrelated cases (75%) (SDHB-GATA29A05-D1S2826-D1S2644 | SDHB-186-130-213), which was observed in only 1 chromosome (1/42) without SDHB exon 1 deletion (X2= 29.43; p < 0.001). Moreover, all cases with SDHB exon 1 deletion had the same gene breakpoint pattern of a 15,678 bp deletion previously described in the Iberian Peninsula, indicating a common origin.

CONCLUSION

The germline heterozygous SDHB exon 1 deletion was the most frequent genetic defect in the Brazilian PPGL cohort. Our findings demonstrated a founder effect for the SDHB exon 1 deletion in Brazilian patients with paragangliomas.

Pathogenesis of Primary Aldosteronism: Impact on Clinical Outcome

Primary aldosteronism (PA) is the most common form of secondary arterial hypertension, with a prevalence of approximately 20% in patients with resistant hypertension. In the last decade, somatic pathogenic variants in KCNJ5, CACNA1D, ATP1A1 and ATP2B3 genes, which are involved in maintaining intracellular ionic homeostasis and cell membrane potential, were described in aldosterone-producing adenomas (aldosteronomas). All variants in these genes lead to the activation of calcium signaling, the major trigger for aldosterone production. Genetic causes of familial hyperaldosteronism have been expanded through the report of germline pathogenic variants in KCNJ5, CACNA1H and CLCN2 genes. Moreover, PDE2A and PDE3B variants were associated with bilateral PA and increased the spectrum of genetic etiologies of PA. Of great importance, the genetic investigation of adrenal lesions guided by the CYP11B2 staining strongly changed the landscape of somatic genetic findings of PA. Furthermore, CYP11B2 staining allowed the better characterization of the aldosterone-producing adrenal lesions in unilateral PA. Aldosterone production may occur from multiple sources, such as solitary aldosteronoma or aldosterone-producing nodule (classical histopathology) or clusters of autonomous aldosterone-producing cells without apparent neoplasia denominated aldosterone-producing micronodules (non-classical histopathology). Interestingly, KCNJ5 mutational status and classical histopathology of unilateral PA (aldosteronoma) have emerged as relevant predictors of clinical and biochemical outcome, respectively. In this review, we summarize the most recent advances in the pathogenesis of PA and discuss their impact on clinical outcome.

Targeted massively parallel sequencing for congenital generalized lipodystrophy

Objective

Our aim is to establish genetic diagnosis of congenital generalized lipodystrophy (CGL) using targeted massively parallel sequencing (MPS), also known as next-generation sequencing (NGS).

Methods

Nine unrelated individuals with a clinical diagnosis of CGL were recruited. We used a customized panel to capture genes related to genetic lipodystrophies. DNA libraries were generated, sequenced using the Illumina MiSeq, and bioinformatics analysis was performed.

Results

An accurate genetic diagnosis was stated for all nine patients. Four had pathogenic variants in AGPAT2 and three in BSCL2. Three large homozygous deletions in AGPAT2 were identified by copy-number variant analysis.

Conclusion

Although we have found allelic variants in only 2 genes related to CGL, the panel was able to identify different variants including deletions that would have been missed by Sanger sequencing. We believe that MPS is a valuable tool for the genetic diagnosis of multi-genes related diseases, including CGL.

Comparative Analysis of Different International Criteria (ACMG-AMP vs. TENGEN) Applied to Classification of Missense Germline Allelic Variants in Patients With Multiple Endocrine Neoplasia Type 1 or Suspected to this Syndrome

Context: Multiple endocrine neoplasia type 1 (MEN1) is a rare autosomal dominant genetic syndrome caused by germline pathogenic allele variants (PAV) in the MEN1 tumor suppressor gene, which predispose MEN1 carriers to the increased risk of several endocrine neoplasms throughout life. The MEN1 gene (11q13), contains 10 exons encoding the MENIN protein. About 600 different PAVs have been reported, with 25% of them being missense variants. Of value, the definition of pathogenicity can be challenging, especially for missense variants. Thus, international guidelines for improving the classification of allele variants were recently defined by the ACMG-AMP (2015). Recently, applying ACMG-AMP criteria with inclusion of clinical features the TENGEN French group suggested modifications aiming to refine the classification of variants in MEN1 syndrome. Objective: To classify missense allelic variants found in the MEN1 gene by the ACMG-AMP guideline using VARSOME and by the TENGEN group to support a comparative analysis of the results obtained with these two methodologies (ACMG-AMP; TENGEN). Methods: the classification of 16 different missense allele variants identified in 17 index cases with or suspected to MEN1 syndrome was conducted according to ACMG-AMP criteria using the VARSOME software followed by the analysis defined by the TENGEN group. Results: Of the 16 variants, 6 were new, 1 was recurrent (2 unrelated index cases) and 9 of them occurred in codons with previous reports of different amino acid exchanges in the same region. Differences observed in the classification by ACMG-AMP and TENGEN were: pathogenic variant (6% vs. 65%); probably pathogenic (88% vs. 12%) and variants of uncertain significance (VUS) (6% vs. 23%). The four VUS classified by TENGEN (one of them for ACMG-AMP) were of sporadic cases without clinical diagnosis of MEN1 (2, for one MEN1-related tumor in early age; 1, for suspected MEN1) or with high risk of phenocopy (1, HPT + acromegaly). Conclusion: The difference observed in the classification of the pathogenicity of these variants, especially due to the higher occurrence of VUS in TENGEN, indicates that the criteria adopted by ACMG-VARSOME would have to be refined for clinical features. By other side, TENGEN apparently reinforce the classification of pathogenicity in cases with clinical diagnosis of MEN1 and reduce the definition of pathogenicity to variants found in MEN1-suspected cases without clinical criteria for the MEN1 diagnosis. These protocols apparently need to be investigate, validated and, probably, improved in other cohorts to reduce risks of misinterpretations and classifications that can, lately, interfere in genetic counseling and in the clinical management of patients. Finally, long-term outcome of cases classified as VUS, functional studies and, familial segregation may reinforce the initial impressions obtained with TENGEN classification.

Comprehensive Analysis of Clinical Features in Index Cases With Multiple Endocrine Neoplasia Type 1 Refine the Risk Rate for Detection of Mutation Distinguishing Negative-Mutation (Phenocopies) and Positive-Mutation Cases

Background: Index cases clinically diagnosed with multiple endocrine neoplasia type 1 (MEN1) are declared as MEN1 phenocopies if no germline MEN1 mutation is identified. In comparison with positive-mutation cases, most phenocopies have been diagnosed in older age, mainly by association of primary hyperparathyroidism (HPT) and pituitary adenoma (PIT), with HPT predominantly diagnosed as uniglandular disease. Besides that, phenocopies rarely develop a third MEN1-related tumor and are associated with lower morbidity and longer survival. However, all these data are mainly derived of genetic studies by Sanger targeted to MEN1 gene from a strict number of MEN1 phenocopies. Objectives: to recognize strong clinical profiles capable of predicting the occurrence or absence of germline MEN1 mutation refining the clinical differentiation of phenocopies and mutation-positive cases before genetic testing disclosure. Casuistic/Methods: 143 MEN1 index cases: 87 MEN1-positive and 56 true MEN1 phenocopies (excluded mutations for MLPA assay and by a mini-painel based on long-range PCR and next generation sequencing of 6 MEN1-related genes (MEN1, p15, p18, p21, p27, AIP) covering full coding and non-coding regions. Results: High detectability rate of MEN1 mutation was associated with the presence of ≥ 4 organs affected for primary tumors (100%), association of HPT/PET (neuroendocrine pancreatic tumor)/PIT (93%), HPT/PET (81%), positive familial history (88% vs. 48%), presence of PET (84%) as malign (80%) as multifocal (95%), two different PETs (100%), multiglandular HPT (81%) and diagnosis of one MEN1-related tumor (93%) or of two/three MEN1 tumors diagnosed before 21y (100%). The combination HPT/PIT has the lowest rate of detection of mutation (33%), it is even lower if PIT was acromegaly (12%) or age at the diagnosis of HPT and PIT was, respectively, > 45y and >30y (8%) and absent if it is added uniglandular HPT (0%) or if there was association HPT/PIT (age-independent) with uniglandular HPT (0%). The prediction for detection of mutation increases if these HPT (> 45y)/PIT (> 30y) cases have multiglandular HPT (20%) and it is 100% with association HPT (< 30y)/PIT (< 21y). A p <0.05 was observed to all data above. Conclusions: By integration of phenotypic clues and full genetic analysis applied to the largest MEN1 phenocopy series, we identified strong clinical predictors capable of anticipate the potential risk rate for mutation detection revealing the estimated chance of an index case harbor a mutation or be classified as phenocopy. By their peculiarities, the management/treatment of phenocopies should potentially be different of that recommended to mutation-positive cases.

Phosphodiesterase 2A and 3B variants are associated with primary aldosteronism

Familial primary aldosteronism (PA) is rare and mostly diagnosed in early-onset hypertension (HT). However, 'sporadic' bilateral adrenal hyperplasia (BAH) is the most frequent cause of PA and remains without genetic etiology in most cases. Our aim was to investigate new genetic defects associated with BAH and PA. We performed whole-exome sequencing (paired blood and adrenal tissue) in six patients with PA caused by BAH that underwent unilateral adrenalectomy. Additionally, we conducted functional studies in adrenal hyperplastic tissue and transfected cells to confirm the pathogenicity of the identified genetic variants. Rare germline variants in phosphodiesterase 2A (PDE2A) and 3B (PDE3B) genes were identified in three patients. The PDE2A heterozygous variant (p.Ile629Val) was identified in a patient with BAH and early-onset HT at 13 years of age. Two PDE3B heterozygous variants (p.Arg217Gln and p.Gly392Val) were identified in patients with BAH and HT diagnosed at 18 and 33 years of age, respectively. A strong PDE2A staining was found in all cases of BAH in zona glomerulosa and/or micronodules (that were also positive for CYP11B2). PKA activity in frozen tissue was significantly higher in BAH from patients harboring PDE2A and PDE3B variants. PDE2A and PDE3B variants significantly reduced protein expression in mutant transfected cells compared to WT. Interestingly, PDE2A and PDE3B variants increased SGK1 and SCNN1G/ENaCg at mRNA or protein levels. In conclusion, PDE2A and PDE3B variants were associated with PA caused by BAH. These novel genetic findings expand the spectrum of genetic etiologies of PA.

Evaluation of SHOX defects in the era of next-generation sequencing

Short stature homeobox (SHOX) haploinsufficiency is a frequent cause of short stature. Despite advances in sequencing technologies, the identification of SHOX mutations continues to be performed using standard methods, including multiplex ligation-dependent probe amplification (MLPA) followed by Sanger sequencing. We designed a targeted panel of genes associated with growth impairment, including SHOX genomic and enhancer regions, to improve the resolution of next-generation sequencing for SHOX analysis. We used two software packages, CONTRA and Nexus Copy Number, in addition to visual analysis to investigate the presence of copy number variants (CNVs). We evaluated 15 patients with previously known SHOX defects, including point mutations, deletions and a duplication, and 77 patients with idiopathic short stature (ISS). The panel was able to confirm all known defects in the validation analysis. During the prospective evaluation, we identified two new partial SHOX deletions (one detected only by visual analysis), including an intragenic deletion not detected by MLPA. Additionally, we were able to determine the breakpoints in four cases. Our results show that the designed panel can be used for the molecular investigation of patients with ISS, and it may even detect CNVs in SHOX and its enhancers, which may be present in a significant fraction of patients.

Genetic diagnosis of congenital hypopituitarism by a target gene panel: novel pathogenic variants in GLI2, OTX2 and GHRHR

AIM

Congenital hypopituitarism has an incidence of 1:3500-10,000 births and is defined by the impaired production of pituitary hormones. Early diagnosis has an impact on management and genetic counselling. The clinical and genetic heterogeneity of hypopituitarism poses difficulties to select the order of genes to analyse. The objective of our study is to screen hypopituitarism genes (candidate and previously related genes) simultaneously using a target gene panel in patients with congenital hypopituitarism.

METHODS

Screening of 117 subjects with congenital hypopituitarism for pathogenic variants in 26 genes associated with congenital hypopituitarism by massively parallel sequencing using a customized target gene panel.

RESULTS

We found three novel pathogenic variants in OTX2 c.295C>T:p.Gln99*, GLI2 c.1681G>T:p.Glu561* and GHRHR c.820_821insC:p.Asp274Alafs*113, and the previously reported variants in GHRHR c.57+1G>A and PROP1 [c.301_302delAG];[c.109+1G>A].

CONCLUSIONS

Our results indicate that a custom-designed panel is an efficient method to screen simultaneously variants of biological and clinical relevance for congenital GH deficiency. A genetic diagnosis was possible in 5 out of 117 (4%) patients of our cohort. We identified three novel pathogenic variants in GHRHR, OTX2 and GLI2 expanding the spectrum of variants associated with congenital hypopituitarism.

Germline mutation landscape of multiple endocrine neoplasia type 1 using full gene next-generation sequencing

Background Loss-of-function germline MEN1 gene mutations account for 75-95% of patients with multiple endocrine neoplasia type 1 (MEN1). It has been postulated that mutations in non-coding regions of MEN1 might occur in some of the remaining patients; however, this hypothesis has not yet been fully investigated. Objective To sequence for the entire MEN1 including promoter, exons and introns in a large MEN1 cohort and determine the mutation profile. Methods and patients A target next-generation sequencing (tNGS) assay comprising 7.2 kb of the full MEN1 was developed to investigate germline mutations in 76 unrelated MEN1 probands (49 familial, 27 sporadic). tNGS results were validated by Sanger sequencing (SS), and multiplex ligation-dependent probe amplification (MLPA) assay was applied when no mutations were identifiable by both tNGS and SS. Results Germline MEN1 variants were verified in coding region and splicing sites of 57/76 patients (74%) by both tNGS and SS (100% reproducibility). Thirty-eight different pathogenic or likely pathogenic variants were identified, including 13 new and six recurrent variants. Three large deletions were detected by MLPA only. No mutation was detected in 16 patients. In untranslated, regulatory or in deep intronic MEN1 regions of the 76 MEN1 cases, no point or short indel pathogenic variants were found in untranslated, although 33 benign/likely benign and three new VUS variants were detected. Conclusions Our study documents that point or short indel mutations in non-coding regions of MEN1 are very rare events. Also, tNGS proved to be a highly effective technology for routine genetic MEN1 testing.

Clinical application of ACMG-AMP guidelines in HNF1A and GCK variants in a cohort of MODY families

Maturity-onset diabetes of the young (MODY) is a form of monogenic diabetes with autosomal dominant inheritance. GCK -MODY and HNF1A -MODY are the prevalent subtypes. Currently, there is growing concern regarding the correct interpretation of molecular genetic findings. The American College of Medical Genetics and Genomics (ACMG) updated guidelines to interpret and classify molecular variants. This study aimed to determine the prevalence of MODY ( GCK / HNF1A ) in a large cohort of Brazilian families, to report variants related to phenotype, and to classify them according to ACMG guidelines. One hundred and nine probands were investigated, 45% with clinical suspicion of GCK -MODY and 55% with suspicion of HNF1A -MODY. Twenty-five different variants were identified in GCK gene (30 probands-61% of positivity), and 7 variants in HNF1A (10 probands-17% of positivity). Fourteen of them were novel (12- GCK /2- HNF1A ). ACMG guidelines were able to classify a large portion of variants as pathogenic (36%- GCK /86%- HNF1A ) and likely pathogenic (44%- GCK /14%- HNF1A ), with 16% (5/32) as uncertain significance. This allows us to determine the pathogenicity classification more efficiently, and also reinforces the suspected associations with the phenotype among novel variants.

TcCYS4, a cystatin from cocoa, reduces necrosis triggered by MpNEP2 in tobacco plants

In Brazil, most cocoa bean production occurs in Southern Bahia. Witches' broom disease arrived in this area in 1989 and has since caused heavy losses in production. The disease is caused by the basidiomycete fungus Moniliophthora perniciosa, a hemibiotrophic fungus that produces the necrosis and ethylene-inducting protein (MpNEP2) during infection; this protein can activate cysteine proteases and induce programmed cell death. Cysteine proteases can be modulated by cystatin. In this study, we overexpressed TcCYS4, a cocoa cystatin, in tobacco plants and evaluated the effect on MpNEP2 in model plants. Tccys4 cDNA was cloned into the pCAMBIA 1390 vector and inserted into the tobacco plants via Agrobacterium tumefaciens. Transgene expression was analyzed by reverse transcription-quantitative PCR and Western blot analysis. Transcript and protein levels in Tcccys4:tobacco lines were 8.9- and 1.5-fold higher than in wild-type plants (wt). Tcccys4:tobacco lines showed no change in growth compared to wt plants. CO2 net assimilation (A) increased in Tcccys4:tobacco lines compared to wt plants. Only one line showed statistically significant stomatal conductance (gs) and transpiration rate (E) changes. MpNEP2 was infiltered into the foliar mesophyll of Tcccys4:tobacco lines and wt plants, and necrotic lesions were attenuated in lines highly expressing Tccys4. Our results suggest that cocoa cystatin TcCYS4 affects MpNEP2 activity related to the progression of programmed cell death in tobacco plants. This may occur through the action of cystatin to inhibit cysteine proteases activated by MpNEP2 in plant tissues. Further studies are necessary to examine cystatin in the Theobroma cacao-M. perniciosa pathosystem.