[Phaeochromocytoma and paraganglioma]. / Phéochromocytome et paragangliome.

Phaeochromocytomas and paragangliomas (PPGL) are rare neuroendocrine tumors that arise from the adrenal medulla or sympathetic and parasympathetic ganglia. These tumors produce most often catecholamines in excess, causing hypertension and sometimes severe acute cardiovascular complications. The diagnosis is based on plasma or urines metanephrines measurements and on conventional and nuclear medicine imaging. Catecholamines-producing PPGL is very unlikely if levels are normal. The diagnosis of PPGL cannot be made without visualization of a tumor. Therapeutic management consists mostly of surgical excision, after drug preparation, and should be done in referral centers. About 40% of pheochromocytomas and paragangliomas occur in the context of an autosomal inherited syndrome, making genetic testing essential. The follow-up must be prolonged because a metastatic evolution or a recurrence can be observed in about 15% of the cases.

A 40-YEAR FOLLOW-UP OF A PATIENT WITH MULTIPLE PARAGANGLIOMAS AND A SDHD MUTATION.

CONTEXT: Germline mutations in Succinate Dehydrogenase Complex Subunit D gene (SDHD) predispose to predominantly benign head and neck and/or thoracic-abdominal pelvic paragangliomas (PGLs). OBJECTIVE: We present the case of a patient carrying a germline SDHD mutation responsible for multiple PGLs, who was followed for 40 years. He was initially diagnosed with a left cervical PGL at the age of 23 years, treated by surgery. Then, he recurred and developed a multifocal disease. The second-line therapeutic option was a three-dimensional conformal radiotherapy performed in 2008. In 2013 the patient had clinical, hormonal, PET- and SPECT-CT data revealing a disease progression. The treatment with the long-acting somatostatin analogue Octreotide Lar was carried out till the patient's death caused by pulmonary embolism in December 2014. RESULTS: Complex treatment led to a long clinical and biochemical remission and control of tumor growth. CONCLUSIONS: Despite their usually benign behavior, multicentric SDHD-related PGLs can require a multimodal approach involving surgery, radiotherapy and medical treatment for providing a long-term control of the disease and maintaining a good quality of life.

Reassessing the clinical spectrum associated with hereditary leiomyomatosis and renal cell carcinoma syndrome in French FH mutation carriers.

We addressed uncertainties regarding hereditary leiomyomatosis and renal cell carcinoma (HLRCC) by exploring all French cases, representing the largest series to date. Fumarate hydratase (FH) germline testing was performed with Sanger sequencing and qPCR/MLPA. Enzyme activity was measured when necessary. We carried out whenever possible a pathology review of RCC and S-(2-succino)-cysteine (2SC)/fumarate hydratase immunohistochemistry. We estimated survival using non-parametric Kaplan-Meier. There were 182 cases from 114 families. Thirty-seven RCC were diagnosed in 34 carriers (19%) at a median age of 40. Among the 23 RCC with pathology review, 13 were papillary type 2. There were 4 papillary RCC of unspecified type, 3 unclassified, 2 tubulocystic, and 1 collecting duct (CD) RCC, all 2SC+ and most (8/10) FH-. Of the remaining 14, papillary type 2, papillary unspecified, CD, and clear cell histologies were reported. The vast majority of RCC (82%) were metastatic at diagnosis or rapidly became metastatic. Median survival for metastatic disease was 18 months (95%CI: 11-29). 133 cases (73%) had a history of cutaneous leiomyomas, 3 developed skin leiomyosarcoma. Uterine leiomyomas were frequent in women (77%), but no sarcomas were observed. Only 2 cases had pheochromocytomas/paraganglioma. CONCLUSION: Our findings have direct implications regarding the identification and management of HLRCC patients.

European Society of Endocrinology Clinical Practice Guideline for long-term follow-up of patients operated on for a phaeochromocytoma or a paraganglioma.

Phaeochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumours. Standard treatment is surgical resection. Following complete resection of the primary tumour, patients with PPGL are at risk of developing new tumoural events. The present guideline aims to propose standardised clinical care of long-term follow-up in patients operated on for a PPGL. The guideline has been developed by The European Society of Endocrinology and based on the Grading of Recommendations Assessment, Development and Evaluation (GRADE) principles. We performed a systematic review of the literature and analysed the European Network for the Study of Adrenal Tumours (ENS@T) database. The risk of new events persisted in the long term and was higher for patients with genetic or syndromic diseases. Follow-up in the published cohorts and in the ENS@T database was neither standardised nor exhaustive, resulting in a risk of follow-up bias and in low statistical power beyond 10 years after complete surgery. To inform patients and care providers in this context of low-quality evidence, the Guideline Working Group therefore prepared recommendations on the basis of expert consensus. Key recommendations are the following: we recommend that all patients with PPGL be considered for genetic testing; we recommend assaying plasma or urinary metanephrines every year to screen for local or metastatic recurrences or new tumours; and we suggest follow-up for at least 10 years in all patients operated on for a PPGL. High-risk patients (young patients and those with a genetic disease, a large tumour and/or a paraganglioma) should be offered lifelong annual follow-up.

Rethinking pheochromocytomas and paragangliomas from a genomic perspective.

Pheochromocytomas (PCC) and paragangliomas (PGL) are rare neuroendocrine tumors of neural crest origin. These tumors are caused by germline or somatic mutations in known susceptibility genes in up to 70% of cases. Over the past few years, the emergence of high-throughput technologies has enabled the unprecedented characterization of genomic alterations in PCC/PGL, and has improved our understanding of the molecular mechanisms that distinguish the different tumor subtypes. Integrated genomic analyses have shown that the mutation status of PCC/PGL susceptibility genes strongly correlates with multi-omics data. These observations not only emphasize the role of the long-standing susceptibility genes as the main drivers of PCC/PGL tumorigenesis, but also illustrate the functional interdependence between genomic and epigenomic alterations. In this review, we discuss the genomic landscape underlying PCC/PGL, its functional consequences for tumorigenesis and tumor progression, and the potential clinical relevance of this knowledge for the application of precision medicine for patients with PCC/PGL.

Immunohistochemical expression of stem cell markers in pheochromocytomas/paragangliomas is associated with SDHx mutations.

OBJECTIVE: Pheochromocytomas (PCCs) are neuroendocrine tumors that occur in the adrenal medulla, whereas paragangliomas (PGLs) arise from paraganglia in the head, neck, thorax, or abdomen. In a variety of tumors, cancer cells with stem cell-like properties seem to form the basis of tumor initiation because of their ability to self-renew and proliferate. Specifically targeting this small cell population may lay the foundation for more effective therapeutic approaches. In the present study, we intended to identify stem cells in PCCs/PGLs. DESIGN: We examined the immunohistochemical expression of 11 stem cell markers (SOX2, LIN28, NGFR, THY1, PREF1, SOX17, NESTIN, CD117, OCT3/4, NANOG, and CD133) on tissue microarrays containing 208 PCCs/PGLs with different genetic backgrounds from five European centers. RESULTS: SOX2, LIN28, NGFR, and THY1 were expressed in more than 10% of tumors, and PREF1, SOX17, NESTIN, and CD117 were expressed in <10% of the samples. OCT3/4, NANOG, and CD133 were not detectable at all. Double staining for chromogranin A/SOX2 and S100/SOX2 demonstrated SOX2 immunopositivity in both tumor and adjacent sustentacular cells. The expression of SOX2, SOX17, NGFR, LIN28, PREF1, and THY1 was significantly associated with mutations in one of the succinate dehydrogenase (SDH) genes. In addition, NGFR expression was significantly correlated with metastatic disease. CONCLUSION: Immunohistochemical expression of stem cell markers was found in a subset of PCCs/PGLs. Further studies are required to validate whether some stem cell-associated markers, such as SOX2, could serve as targets for therapeutic approaches and whether NGFR expression could be utilized as a predictor of malignancy.

Screening in asymptomatic SDHx mutation carriers: added value of ¹8F-FDG PET/CT at initial diagnosis and 1-year follow-up.

PURPOSE: Specific recommendations on screening modalities for paraganglioma (PGL) and phaeochromocytoma (PCC) in asymptomatic SDHx mutation carriers (relatives) are still lacking. We evaluated the added value of (18)F-FDG PET/CT in comparison with morphological imaging at initial diagnosis and 1 year of follow-up in this population. METHODS: The study included 30 consecutive relatives with a proven SDHx mutation who were investigated by (18)F-FDG PET/CT, gadolinium-enhanced magnetic resonance angiography of the head and neck, thoracic/abdominal/pelvic (TAP) contrast-enhanced CT and/or TAP MRI. (123)I-MIBG scintigraphy was performed in 20 subjects and somatostatin receptor scintigraphy (SRS) in 20 subjects. The gold standard was based on pathology or a composite endpoint as defined by any other positive imaging method and persistent tumour on follow-up. Images were considered as false-positive when the lesions were not detected by another imaging method or not confirmed at 1 year. RESULTS: At initial work-up, an imaging abnormality was found in eight subjects (27%). The final diagnosis was true-positive in five subjects (two with abdominal PGL, one with PCC and two with neck PGL) and false-positives in the other three subjects (detected with (18)F-FDG PET/CT in two and TAP MRI in one). At 1 year, an imaging abnormality was found in three subjects of which one was an 8-mm carotid body PGL in a patient with SDHD mutaion and two were considered false-positive. The tumour detection rate was 100% for (18)F-FDG PET/CT and conventional imaging, 80% for SRS and 60% for (123)I-MIBG scintigraphy. Overall, disease was detected in 4% of the subjects at the 1-year follow-up. CONCLUSION: (18)F-FDG PET/CT demonstrated excellent sensitivity but intermediate specificity justifying combined modality imaging in these patients. Given the slow progression of the disease, if (18)F-FDG PET/CT and MRI are normal at baseline, the second imaging work-up should be delayed and an examination that does not expose the patient to radiation should be used.

Malignant head/neck paragangliomas. Comparative study.

BACKGROUND: The objective of this study was to report 11 cases of malignant head and neck paraganglioma and to compare their epidemiological, clinical, and genetic characteristics, their natural history and their treatment with those of a series of 131 benign paragangliomas. PATIENTS AND METHODS: Retrospective analysis of 142 patients with head and neck paraganglioma managed between 2001 and 2008. Age at the time of diagnosis, gender, primary tumour site, presence of other non-head/neck paragangliomas and/or metastases diagnosed by imaging (CT, MRI, Octreoscan or (18)F-FDG PET), histology, urinary catecholamine and metanephrine levels, family history, and genetic test results were recorded. RESULTS: This series comprised 131 benign head and neck paragangliomas, mostly observed in women with a mean age at diagnosis of 45 years and a predominance of tympanojugular sites (followed by carotid and vagal sites) with 5% of secreting tumours and 20% of multifocal tumours. Eleven patients (7.7%) with a 1:1 sex ratio presented criteria of malignancy. These patients, with a lower mean age (38 years), predominantly presented carotid lesions with a higher rate of secreting and multifocal tumours, 27% and 46% respectively. The main sites of metastases were bone and lymph nodes. No tympanic paragangliomas were observed. CONCLUSIONS: Malignant paragangliomas are mainly observed in young patients with multifocal tumours, particularly carotid tumours, and are predominantly related to subunit SDH-B mutation. The work-up in these high-risk patients must include whole body scintigraphy and spine MRI. Malignancy is not necessarily associated with a poor short-term prognosis due to the slow course of the disease.

The genetics of paragangliomas.

Over the last decade, it has been clearly established that one-third of all paragangliomas are genetically determined. Genetic testing, guided by the family history and clinical findings, must now be proposed to all subjects undergoing surgery for head and neck paraganglioma. When a mutation is identified on one of the susceptibility genes (SDHD, SDHB, SDHC, SDHAF2, VHL), at-risk subjects should be investigated for the presence of other supra- and infradiaphragmatic paragangliomas and functional catecholamine-secreting paragangliomas and/or phaeochromocytomas. Identification of a germline mutation on the SDHB gene is a high-risk factor for malignancy and poor prognosis and requires close surveillance of subjects carrying this mutation. The diagnosis of hereditary paraganglioma also allows predictive genetic screening in first-degree relatives of the index subject. Genetic testing for paraganglioma is therefore now an important component of the diagnostic and therapeutic management of these patients.

Presymptomatic genetic testing in minors at risk of paraganglioma and pheochromocytoma: our experience of oncogenetic multidisciplinary consultation.

The aim of the work was to define quality criteria for presymptomatic genetic testing in minors at risk of paraganglioma/pheochromocytoma. A 3-step multidisciplinary procedure was developed: 1) preparatory consultations for parents, providing decision support and advice concerning the way of informing the children; 2) consultation with the minor and blood sampling; and 3) announcement of the result of the genetic test to the minor and his/her parents. Twenty-three minors (mean age=9.22) were tested. The result was positive in 16 cases (presence of the familial mutation) and negative in 7. The 23 procedures were classified according to emotional reactions at the announcement of the result: calm (18/23) or tense (5/23). In parallel, 4 criteria for a good testing procedure was defined: 1) both parents agreeing to have their child tested when they felt ready; 2) parents being given advice concerning the way to inform their child; 3) the most appropriate time for testing being discussed for each child; and 4) avoidance of testing during medical examination periods for the carrier parent. The frequencies of the above criteria were as follows: 1 (17/23); 2 (19/23); 3 (17/23); and 4 (17/23). The overall quality of the testing procedure, calculated as the sum of the four criteria, differed significantly between calm and tense announcements (p<0.01). This study highlights the important role of careful preparation with the parents in emotional acceptance of the result of testing. The 4 criteria identified should be evaluated in further prospective studies.

A decade (2001-2010) of genetic testing for pheochromocytoma and paraganglioma.

The identification of 9 susceptibility genes for paraganglioma/pheochromocytoma between 2001 and 2010 has led to the development of routine genetic tests. To study the evolution in genetic screening for paraganglioma/pheochromocytoma over the past decade, we carried out a retrospective study on the tests performed in our laboratory from January 2001 to December 2010. A genetic test for paraganglioma/pheochromocytoma was assessed for 2 499 subjects, 1 620 index cases, and 879 presymptomatic familial genetic tests. A germline mutation in a PGL/PCC susceptibility gene was identified in 363 index cases (22.4%): 269 in SDHx genes (137 in SDHB, 100 in SDHD, 30 in SDHC, 2 in SDHA), 64 in VHL, 23 in RET, and 7 in TMEM127. A presymptomatic paraganglioma/pheochromocytoma test was positive in 427 subjects. Advances in molecular screening techniques led to an increase in the total number of mutation-carriers diagnosed each year. Overall, during the last decade, our laboratory identified a germline mutation in 44.7% of patients with a suspect hereditary PGL/PCC and in 8% of patients with an apparently sporadic PGL/PCC. During the past decade, the discoveries of new paraganglioma/pheochromocytoma susceptibility genes and the subsequent progress of molecular screening techniques have enabled us to diagnose a hereditary paraganglioma/pheochromocytoma in about 22% of patients tested in routine practice. This genetic testing is of major importance for the follow-up of affected patients and for the genetic counselling of their families.

Long-term postoperative follow-up in patients with apparently benign pheochromocytoma and paraganglioma.

Patients with pheochromocytoma or paraganglioma are at risk of developing tumor recurrences or new tumors after successful resection of the primary tumor. This review summarizes current knowledge concerning the incidence and risk factors for such events. The overall incidence exceeds 15%. Patients with inherited tumors have a higher probability of recurrence or new tumors. Most recurrences are metastatic, particularly in patients with SDHB mutations or nonhereditary tumors. We recommend the determination of plasma or urinary metanephrines (normetanephrine and metanephrine) 1 month after surgery. In patients with sporadic, single tumors ≤5 cm in diameter, clinical and biochemical follow-up should be performed every 2 years. However, this follow-up period can be reduced to yearly, if it is more simple and more convenient for patients and physicians. Patients with larger or multiple but apparently benign tumors and/or inherited disease should be tested 6 months after surgery and then every year for the rest of their lives. Imaging follow-up is also required in patients with inherited or malignant tumors.

An update on the genetics of paraganglioma, pheochromocytoma, and associated hereditary syndromes.

Pheochromocytomas (PCCs) and paragangliomas (PGLs) are catecholamine-secreting tumors of neural crest origin. Once collectively known as the '10% tumor', based on the frequency of inherited forms of the disease, they are now referred to as the '10-gene tumor', based on the number of susceptibility genes identified to date. Most familial cases of pheochromocytoma and/or paraganglioma and 10-20% sporadic cases carry germline mutations in VHL, RET, NF1, SDHA, SDHB, SDHC, SDHD, SDHAF2, TMEM127, or MAX. The finding of somatic mutations in VHL and RET in an additional 10-15% of tumors has brought the proportion of all patients with PCC and/or PGL due to a genetic disruption in these genes to approximately one half. These findings impact on the clinical management of patients. The diversity in the genetic etiology has transcription correlates, which are reflected in the 2 main transcription signatures underlying these mutations: a pseudohypoxic cluster (VHL and SDH gene mutation carriers) and a cluster rich in kinase receptor signaling and protein translation pathways (RET, NF1, TMEM127 and MAX mutation carriers). Recognition of these clusters offers clues to better understand tumor pathogenesis as well as a rationale for the development of targeted therapies. In this report we provide an overview of the transcription-based classification of PCCs and PGLs, an update on the more recently identified susceptibility genes and an outline of current gaps in this research field as well as challenges for the coming years.

Evaluation of a standardized protocol for processing adrenal tumor samples: preparation for a European adrenal tumor bank.

Storage and tissue handling of surgical tumor specimen have been recognized as critical steps that can potentially affect reproducibility and comparability of molecular endpoints between laboratories. In the preparation of adrenal tumor tissue banking, three different protocols that simulate warm ischemia upon tumor removal (protocol I), thawing and refreezing cycles (protocol II), as well as storage of vital tumor samples (protocol III) were applied. For the first two protocols, samples were subdivided and either snap frozen or treated with a RNA preserving agent (RPA) while in protocol III different storage media were compared. Following these procedures, recovery and integrity of DNA, RNA, and protein by means of pulsed field electrophoresis, long-range PCR, real-time PCR, immunoblot, and immunohistochemistry (protocol I and II) as well as cell viability and steroidogenic capacity (protocol III) were investigated. While DNA integrity was not influenced by different treatment modalities, expression levels of adrenal marker genes were more affected in samples after snap freezing in comparison to RPA pretreatment. Moreover, storage at room temperature before and after freezing could be demonstrated to decrease the relative amount of protein phosphorylation (ERK) and enzymatic activity (succinate cytochrome c reductase) while overall protein levels were not significantly affected. Similarly, morphological or immunohistochemical evaluation was comparable between groups. For primary cell cultures generated after storage of tumor samples similar rates of viability were observable while steroid output varied between the groups. Overall, on the basis of the presented endpoints standardized operational procedures can be defined for a proposed European adrenal tumor biobank.

Penetrance and clinical consequences of a gross SDHB deletion in a large family.

Mutations in the gene encoding subunit B of the mitochondrial enzyme succinate dehydrogenase (SDHB) are inherited in an autosomal dominant manner and are associated with hereditary paraganglioma (PGL) and pheochromocytoma. The phenotype of patients with SDHB point mutations has been previously described. However, the phenotype and penetrance of gross SDHB deletions have not been well characterized as they are rarely described. The objective was to describe the phenotype and estimate the penetrance of an exon 1 large SDHB deletion in one kindred. A retrospective and prospective study of 41 relatives across five generations was carried out. The main outcome measures were genetic testing, clinical presentations, plasma catecholamines and their O-methylated metabolites. Of the 41 mutation carriers identified, 11 were diagnosed with PGL, 12 were found to be healthy carriers after evaluation, and 18 were reportedly healthy based on family history accounts. The penetrance of PGL related to the exon 1 large SDHB deletion in this family was estimated to be 35% by age 40. Variable expressivity of the phenotype associated with a large exon 1 SDHB deletion was observed, including low penetrance, diverse primary PGL tumor locations, and malignant potential.

Inheritance of arterial lesions in renal fibromuscular dysplasia.

We have previously shown that patients with renal fibromuscular dysplasia (FMD) have asymptomatic carotid lesions and that familial forms may occur. The objective of this study was to test whether carotid lesions could be detected in relatives of familial cases. High-resolution echotracking of the carotid artery was performed in 47 relatives of 13 cases from six families. This non-invasive investigation led to a semiquantitative arterial score that was compared with that obtained for 47 controls matched for age and sex and that for 125 sporadic cases. Familial resemblance was tested by using a generalized estimating equation approach taking into account the clustering of scores in families. As expected, FMD cases had a significantly higher score than controls (4.02 vs 2.52, P<10(-5)). Familial cases were not significantly different from sporadic cases. Of interest, the 47 apparently healthy relatives of familial cases had also a high carotid score (4.17), very significantly higher than that of controls (2.52, P<10(-5)) even though lower than the corresponding index FMD cases (4.81, P=0.01). Segregation analysis showed that 52% of the descendants of subjects with a score >4 had a score >4, a proportion consistent with autosomal-dominant transmission of the trait. Altogether these results strengthen the hypothesis of renal FMD being a systemic arterial disease and argue for a familial resemblance that may be due to a major genetic effect. The carotid score obtained by high-resolution echotracking may provide a non-invasive surrogate marker for renal FMD of potential value for use in linkage strategies on large pedigrees.

[Malignant hereditary paraganglioma: problems raised by non-functional forms management]. / Paragangliomes malins héréditaires: problèmes liés à la prise en charge des formes non sécrétantes.

Non-functional paraganglioma have not clinical or biological characteristics, so that the diagnostic is most of the time delayed and made on the occasion of advanced abdominal tumor or symptomatic metastasis management. Hereditary forms, notably those with SDHB mutation, seem to have a poor prognosis. On the other hand, and on the oposite to sporadic forms, they are the only ones to benefit from genetic testing which make possible, if positive, an earlier diagnostic, before apparition of symptoms, recurrence or metastasis. We report a case of non-functional malignant hereditary paraganglioma diagnosed belatedly and we will consider management problems raised by non-functional forms.

New insights in the genetics of adrenocortical tumors, pheochromocytomas and paragangliomas.

Recent advances in the molecular genetic of adrenal tumors give new insights in the pathophysiology of these neoplasms in both hereditary and sporadic cases. The practice of genetic counselling in patients with adrenal tumors have been recently changed by the identification and the understanding of new specific hereditary cancer susceptibility syndromes. In the case of sporadic adrenocortical tumors these progress also offer new prognosis predictors. The genetic predisposition to adrenocortical cancer in children has been well established in the Li-Fraumeni and Beckewith-Wiedeman syndromes due to germline p53 mutation located at 17p13 and dysregulation of the imprinted IGF-2 locus at 11p15, respectively. Adrenocortical tumors are also observed in Multiple Endocrine Neoplasia type I syndrome. Cushing's syndrome due to primary pigmented nodular adrenocortical disease have been observed in patients with germline PRKAR1A inactivating mutations. Interestingly allelic loss at 17p13 and 11p15 have been observed in sporadic adrenocortical cancer and somatic PRKAR1A mutations in secreting adrenocortical adenomas. The potential interest of these finding for the diagnosis of these tumors will be discussed. In the case of pheochromocytoma and paraganglioma, the demonstration that three genes encoding three succinate dehydrogenase subunits (SDHD, SDHB, SDHC), belonging to the complex II of the respiratory chain in the mitochondria, are involved in the genetics of familial and especially in apparently sporadic phaeochromocytomas have dramatically modified our practice. Up to date, four diagnosis of familal disease (multiple endocrine neoplasia type II, von Hippel Lindau disease, neurofibromatosis type 1 and hereditary paraganglioma) should be discussed and causative mutations in six different phaechomocytoma susceptibility genes (RET, VHL, NF1, SDHB, SDHD, SDHC) could be identified. In this review, we will perform an update compiling these new clinical, genetic and functional data recently published. We will suggest guidelines for the practice of the phaeochomocytoma genetic testing in the patients and their families, and for an early detection of tumors in the patients or in individuals determined to be at-risk of disease by the presymptomatic genetic testing.

[Genetics and essential hypertension: candidate genes or screening of the whole genome?]. / Génétique et hypertension artérielle essentielle: gènes candidats ou criblage du génome entier?

Essential hypertension is a major cardiovascular risk factor in the industrialised countries. Its hereditary nature has been well established in many familial studies: about 30% of blood pressure variance is thought to be genetically determined. However, the identification of the culprit genes has met with many difficulties: the multitude of genes, the effect of which is difficult to appreciate, the many possible genetic polymorphisms of each gene studied, the very important role of environmental factors (diet, physical activity, etc...) on the blood pressure itself or on the effect of the genes which control the blood pressure. With the exception of some rare caricatural forms of mendelian transmitted hypertension, the search for genes has focused on large case control studies and/or studies of siblings with hypertension. Two main approaches are used with these collections of subjects. The first consists of analysing so-called "candidate" genes which code for proteins whose function is known and which may influence the blood pressure. In the last ten years, many candidate genes have been assessed with often controversial results. The second approach is to carry out, with no a priori, a complete screen of the genome. These more recent studies have also provided contradictory results. To date, the results illustrate the difficulty of genetic analysis of a complex trait and the necessity of more integrated approaches: analysis of combination of polymorphisms, analysis of a phenotype under standardised environmental conditions, analysis of gene-environment interactions.