a germline mutation in the von - hippel lindau ( vhl ) gene predisposes carriers to development of abundantly vascularised tumours in multiple organs . these tumours may include haemangioblastoma in the retina ( also referred to as retinal angioma ) , cerebellum and myelum , renal cell carcinoma ( clear cell type ) , phaeochromocytoma , islet cell tumours of the pancreas , and endolymphatic sac tumours , as well as cysts and cystadenoma in the kidney , pancreas , epididymis and broad ligament ( fig . 1 ) [ 1 - 3 ] . vhl disease is an autosomal , dominant inherited tumour syndrome with an estimated prevalence of 2 - 3 per 100,000 persons ( omim # 193300 ) . at present , metastases from renal cell carcinoma and neurological complications from cerebellar haemangioblastoma are the most common causes of death . virtually all cases of classic vhl disease are identified , enabling early and presymptomatic diagnosis in families . subsequently , periodical clinical examination and advanced operation techniques are likely to reduce both morbidity and mortality in patients with vhl disease . in the presence of a positive family history , vhl disease can be diagnosed clinically in a patient with at least one typical vhl tumour . typical vhl tumours are retinal , spinal and cerebellar haemangioblastoma , renal cell carcinoma , and phaeochromocytoma . endolymphatic sac tumours and multiple pancreatic cysts suggest a positive carriership ( in the presence of a positive vhl family history ) , since they are uncommon in the general population . in contrast , renal and epididymal cysts occur frequently in the general population and are , as sole manifestation , not reliable indicators for vhl disease . in patients with a negative family history of vhl - associated tumours , a diagnosis of vhl disease can also be made when they exhibit two or more haemangioblastomas , or a single haemangioblastoma in association with another typical manifestation . the gene that , in mutated form , is responsible for the disease is located on chromosome 3 ( 3p25 - 26 ) . the vhl gene is a relatively small gene that covers approximately 14,500 basepairs of genomic dna . the vhl gene encodes a ubiquitously expressed messenger rna of 4,700 nucleotides and the protein - coding region is contained in three exons . germline mutation analysis has revealed two mutation hotspots that concur with important functional domains of the vhl protein ( fig . 2 ) . functional domains of the vhl protein and distribution of germline mutations ( from vhl database ) . hotspots for mutations are readily visible at amino acids 67 - 117 , hypoxia - inducible factor ( hif)-1 binding domain ( in the -domain ) and 157 - 170 , elongin c ( eloc ) binding domain ( in the -domain ) . copyright 2003 , the endocrine society   the vhl gene is a tumour suppressor gene according to knudson 's ' two - hit ' hypothesis : for a normal cell , inactivation of both copies of the vhl gene is required to develop into a tumour cell . in carriers of a vhl gene germline mutation , tumours tend to occur multicentrically and bilaterally , and manifest at a younger age than in patients without a vhl gene germline mutation , where each of the two vhl gene alleles in a cell has to become affected by an independent hit at the somatic level . the vhl gene encodes a 213 amino acid protein that does not closely resemble any other human protein . the vhl protein resides predominantly in the cytoplasm and is widely expressed in normal human tissues . strong expression is detected in target tissues of the disease , such as cerebellar purkinje cells , proximal and distal renal tubules and exocrine pancreas . the vhl protein is also expressed in organs not at risk for the disease , such as the pituitary gland , colon and thyroid . foetal mice deprived of both copies of the vhl gene are not viable . in human embryos , the vhl protein is expressed in all three germ layers . the well - vascularised phenotype of vhl tumours suggests that inactivation of the vhl gene induces either upregulation of an angiogenic factor or downregulation of an inhibitor of angiogenesis . in vhl - associated haemangioblastoma and renal cell carcinoma , various proteins that are involved in angiogenesis these angiogenic proteins include vascular endothelial growth factor ( vegf ) , plasminogen activator inhibitor 1 ( pai-1 ) and erythropoietin [ 10 - 12 ] . the genes coding for these proteins have in common that they are regulated by hypoxaemia . during hypoxaemia a transcription factor , hypoxia - inducible factor ( hif)-1 , binds to the promoters of these genes and stimulates their transcription . in normoxic conditions 3 ) . the -domain of the vhl protein binds to elongin c , which is connected with elongin b in a multi - protein complex ( fig . 3 ) . this complex targets the hif-1 substrate for degradation in a proteasome via a process called ubiquitination . consequently , excessive blood vessel formation may occur when hypoxia - inducible proteins are not properly degraded . in other words , in cells lacking wild - type vhl protein , degradation of hif-1 is impaired and thus those cells behave as if they were deprived of oxygen . in addition to the regulation of hif-1 , the vhl protein has been demonstrated to interact with fibronectin and urokinase , which are required for extracellular matrix formation . the vhl protein and oxygen - dependent ubiquitination of the hypoxia - inducible factor ( hif)-1. the vhl protein contains two functional domains : alpha (  ) and beta (  ) . the -domain of the vhl protein binds to elongin c , which is connected with elongin b in a multi - protein complex consisting of cul2 , rbx1 and e2 ubiquitin conjugating enzyme ( e2 ) . the -domain directly binds the substrate , hif-1. the vhl protein directs , depending on the amount of available oxygen , the breakdown ( ubiquitination ) of hif-1 in the proteasome . in normoxic circumstances , hif-1 is hydroxylated and binds to an intact vhl protein and is ubiquitinated in the proteasome ( left ) . during hypoxic circumstances the non - hydroxylated hif-1 does not bind to the vhl protein and accumulates ( right ) . in the case of a defect or absent vhl protein subsequently , genes that are regulated by hif-1 , like vascular endothelial growth factor ( vegf ) and erythropoietin ( epo ) , are upregulated , leading to ( neo ) angiogenesis and tumour growth . the relationship between the presence of a vhl germline mutation and the occurrence of one or more vhl - related tumours is a well - established observation in the literature . only scarce evidence is provided for reduced or even non - penetrance of some vhl germline mutations . the mean prevalence of vhl - associated tumours is depicted in figure 1 . generally , vhl gene germline mutation carriers present tumours at a relatively young age . the mean age at diagnosis ( with intervals ) for vhl tumours are : retinal haemangioblastoma 25 years ( 1 - 68 ) , phaeochromocytoma 30 years ( 5 - 56 ) , cerebellar haemangioblastoma 30 years ( 9 - 78 ) , and renal cell carcinoma 35 - 40 years ( 15 - 69 ) [ 1 - 5 ] . based upon clinical expression of the disease , vhl disease has been divided into four subtypes , with a central role for phaeochromocytoma ( table 1 ) . type 2 families have phaeochromocytomas and are divided into subtypes with a low ( 2a ) or high risk ( type 2b ) of renal cell carcinoma , while type 2c families present with phaeochromocytoma only . in addition to evidence for interfamilial variability , also intrafamilial variability is a well - observed characteristic in vhl disease . this observation indicates that other genetic ( ' modifier ' genes ) and/or environmental factors are involved in the clinical manifestations of vhl germline mutations . apparently , there is no simple relationship between a germline mutation in the vhl gene and the manifestation ( age of onset and type ) of vhl - related tumours . genotype - phenotype correlation for von hippel - lindau disease and possible responsible pathophysiological mechanism hab , haemangioblastoma ; cns , central nervous system ; rcc , renal cell carcinoma ( clear cell type ) ; phaeo , phaeochromocytoma ; hif , hypoxia - inducible factor ; + , tumour present ; - , tumour absent whereas vhl disease manifests itself as an autosomal dominant trait , it can be considered as a recessive trait at the cellular level . similar to other hereditary tumours caused by germline inactivation of a tumour suppressor gene , vhl tumours arise by a loss of the wild - type vhl allele , while maintaining the mutated allele . such loss of heterozygosity ( loh , caused by deletion , non - disjunction , somatic recombination , etc . ) at the vhl locus has been demonstrated in most vhl disease associated tumours . apart from loh , other mechanisms of somatic inactivation of the vhl gene ( point mutations , promoter hypermethylation ) have also been observed in these tumours . in non - familial ( vhl - related ) tumours , tumourigenesis is thought to be initiated by independent somatic alteration of both alleles of the vhl tumour suppressor gene . somatic vhl gene mutations and allele loss are indeed frequent events in sporadic clear cell renal cell carcinoma and sporadic haemangioblastoma , but are uncommon in sporadic ( i.e. non - tumour syndrome associated ) phaeochromocytoma . so far , there is no evidence for downregulation of an inhibitor of angiogenesis in vhl tumourigenesis . the abundant vascularisation of haemangioblastoma and renal cell carcinoma can be readily explained with the hif-1 and ubiquitination theory as described above . loss of vhl function reduces hif-1 degradation and increases vegf expression , which leads in turn to angiogenesis . in general , protein truncating mutations and missense mutations in the -domain of the vhl protein , predicting a loss of function , seem to be associated with vhl type 1 ( fig . 2 and table 1 ) . in contrast , putative gain of function mutations are associated with vhl type 2c , involving non - excessively vascularised phaeochromocytoma only . vhl type 2c families are predominantly associated with specific missense mutations , notably in the -domain . in type 2a and type 2b , mutations hamper either the binding to elonginc by the -domain of vhl or the capture of target proteins by the -domain of vhl . consequently , such target proteins ( e.g. hif-1 ) can not be properly degraded in the proteasome . phenotypes 2a and 2b have , next to a low or high risk of renal cell carcinoma , respectively , development of both haemangioblastoma and phaeochromocytoma . the co - occurrence of these two kinds of tumours is a consequence of a single amino acid substitution in the vhl protein but is putatively caused by opposing tumourigenic mechanisms ( i.e. gain of function and loss of function ) . previously , we have hypothesized that this apparent discrepancy might be explained by tissue - specific vhl dosage effects , possibly in combination with tissue - specific involvement of other proteins mediating hif1- degradation . vhl gene germline mutations are detected in virtually all classic families with more than one affected family member , or classic sporadic patients with multiple vhl - related tumours . moreover , vhl gene germline mutations are identified in 4% of patients with apparently sporadic haemangioblastoma , in 1.6% with renal cell carcinoma and in 3% to 9% with phaeochromocytoma [ 18 - 21 ] . so , vhl gene germline mutations are not only identified in patients who do meet clinical diagnostic criteria , but also in patients with one or more vhl tumour and/or without a negative family history . this may occur when there is 1 ) incomplete family history data ; 2 ) non - penetrance of a germline mutation in one of the parents ; 3 ) a ' de novo ' mutation . de novo mutations occur in approximately 20% of the identified vhl gene germline mutation carriers . the mutation spectrum is heterogeneous , with mutations scattered throughout most of the vhl gene ( fig . 2 ) . missense mutations are found in 40% of the families with an identified vhl gene germline mutation . microdeletions ( 1 - 18 nucleotides ) , insertions ( 1 - 8 nucleotides ) , splice site and nonsense mutations , all predicted to lead to a truncated protein , are found in 30% of the families . large deletions ( deletions encompassing the entire gene ) account for the remaining 30% of the vhl gene germline mutations . since the size of the protein - encoding region of the vhl gene is small , it seems justified to perform screening for point mutations for vhl always by direct nucleotide sequence analysis of the entire protein - encoding region and splice - junctions . deletions are readily detected with ' southern blotting ' and ' fluorescence in situ hybridization ' ( fish ) , and more recently using ' multiple ligation - dependent probe amplification ' ( mlpa , http://www.mrc-holland.com ) . both clinical geneticists and consulting physicians may request genetic testing in a symptomatic patient for the confirmation of a clinical diagnosis . however , consultation of a clinical geneticist is indicated before a genetic test is to be performed because a molecular genetic diagnosis may have consequences for both the index patients and their family members . moreover , the experience of a clinical geneticist may be needed for a correct interpretation of the test result . persons eligible for vhl gene germline mutation analysis because genetic counselling entails many aspects , such as information about psychological and social consequences , presymptomatic tests should preferably be performed by clinical geneticists . clinical monitoring ( table 3 ) should be primarily organized around those vhl patients who have tested positive for a vhl gene germline mutation . in addition , the following persons should be monitored : first- and second - degree family members in a vhl family without an identified germline mutation ; first- and second - degree family members that decline a dna test ; patients ( and first - degree family members ) with a typical vhl tumour and features that suggest the presence of a germline mutation ( i.e. the presence of multi - centric or bilateral tumours , involvement in more than one organ , a suspected family history and young age at diagnosis ) . with the involvement of many organs in vhl disease , it is of utmost importance that periodic monitoring is carried out in a well - co - ordinated , multidisciplinary team of physicians . on the basis of present knowledge of genotype - phenotype correlations in vhl disease however , regarding phaeochromcyotoma , we feel periodic monitoring could be less frequent in vhl type 1 and more frequent in vhl type 2 . vhl protocol for periodic clinical surveillance * accumulating evidence suggests that measurements of plasma - free metanephrines or urinary - fractionated metanephrines ( normetanephrine and metanephrine separately ) are the most sensitive tests for diagnosis , and are the most suitable for reliable exclusion of phaeochromocytoma . * * radiosurgical techniques have been developed that enable presymptomatic treatment of solid cerebellar haemangioblastoma , which may justify ( more frequent ) periodical surveillance for these tumours . * * * when an mri of the myelum is made every two years it is recommended to image the upper abdominal organs simultaneously . in this way the upper abdomen is monitored with ultrasound and mri in alternate years . * * * * when an endolymphatic sac tumour ( elst ) is suspected ; i.e. hearing loss / deafness , tinnitus , or vertigo . so far , only a small number of guidelines for the treatment of vhl - associated tumours have been developed . most commonly , a choice is made between conservative policy ( surveillance of tumours ) and surgery . options for treatment range from bilateral nephrectomy , nephron - sparing surgery to follow - up investigations only . if both kidneys are affected with multiple cysts and tumours , a difficult decision has to be made between radical nephrectomy or nephron - sparing surgery . whenever feasible , nephron - sparing surgery is performed in order to maintain renal function as long as possible . haemangioblastomas are regarded as benign and slow - growing tumours that do not normally invade the surrounding brain . however , complications may arise due to the tumour 's tendency to form expanding cysts . cerebellar shift may lead to herniation of the cerebellar tonsils through the foramen magnum and subsequently elevated or even life - threatening intracranial pressure . the standard treatment is complete microsurgical removal , aided if necessary by preoperative embolisation to reduce the tumour 's vascularity . a new technique , stereotactic radiosurgery , offers the possibility of tackling multiple cerebellar lesions in a single treatment , which is particularly important in vhl patients . radiosurgery shrinks , or stops the growth of , small- or medium - sized ( i.e. smaller than 3 cm ) solid haemangioblastomas . adjoining cysts , however , do not respond to radiosurgery and require later , sometimes repeated , evacuation . since early detection , periodic clinical surveillance and timely treatment of vhl patients lead to a better prognosis , information on the possibility of dna analysis has to be provided to all family members . for privacy reasons , it is not allowed for health care workers to contact family members of vhl patients directly . with information brochures ( spread via the patient or informed family members ) persons at risk for vhl disease can be informed and advised to seek genetic counselling themselves . in this way they have a free choice for themselves , whether they ( or their offspring ) want to be tested . patients can turn to vhl support groups for support in emotional distress , information , and advice on social issues ( see : http://www.vhl.org ) .
a germline mutation in the von - hippel lindau ( vhl ) gene predisposes carriers to development of abundantly vascularised tumours in the retina , cerebellum , spine , kidney , adrenal gland and pancreas . 
 most vhl patients die from the consequences of cerebellar haemangioblastoma or renal cell carcinoma . 
 the vhl gene is a tumour suppressor gene and is involved in angiogenesis by regulation of the activity of hypoxia - inducible factor 1- ( hif1- ) . 
 clinical diagnosis of vhl can be confirmed by molecular genetic analysis of the vhl gene , which is informative in virtually all vhl families . 
 a patient with ( suspicion for ) vhl is an indication for genetic counselling and periodical examination .