Von Hippel-Lindau syndrome. A pleomorphic condition

Von Hippel-Lindau (VHL) syndrome (OMIM 193300) is an autosomal dominant disorder caused by deletions or mutations in a tumor suppressor gene mapped to human chromosome 3p25. It is characterized clinically by vascular tumors, including retinal and central nervous system hemangioblastomas (cerebellar, spinal, and brain stem). Hemangioblastomas are benign and do not metastasize. Other features include cysts of the kidneys, liver, and pancreas. Clear cell renal cell carcinoma occurs in up to 70% of patients with VHL and is a frequent cause of death. Pheochromocytomas occur in association with specific alleles of the VHL gene; therefore, a family history of pheochromocytoma in association with VHL is an indication for thorough surveillance for pheochromocytoma in affected family members. Recently, it has been appreciated that patients with VHL may develop endolymphatic sac tumors, which can cause tinnitus or deafness. The diagnosis of VHL may be made in a patient with a family history of VHL based on a single retinal or cerebellar hemangioblastoma, renal cell carcinoma or pheochromocytoma, and, possibly, multiple pancreatic cysts. Renal and epididymal cysts are not sufficient to make the diagnosis of VHL. In the absence of a family history of VHL the presence of two or more retinal or cerebellar hemangioblastomas, or one hemangioblastoma with one visceral tumor, is required for diagnosis. Studies of the natural history of VHL showed a life expectancy less than 50 years before surveillance protocols were developed. Annual assessments (physical and ophthalmologic examinations) should begin in infancy. Imaging of abdominal organs and the brain and spine should be added in teenagers and adults. Renal cysts and tumors should be monitored by computed tomography every 6 months. Mutation analysis has allowed presymptomatic identification of affected family members; those found not to have inherited the gene do not need to be monitored. The VHL gene coding sequence contains three exons, and two isoforms of mRNA exist, reflecting the presence or absence of exon 2. Tumors arise after the loss or inactivation of the wild type allele in a cell. About 20% of patients have large germline mutations detectable by Southern blot analysis, 27% have missense mutations, and 27% have nonsense or frameshift mutations. In about 20% of VHL families no deletion or mutation can be detected. Families may be characterized by the presence (type 2; 7% to 20% of families) or absence (type 1) of pheochromocytomas. Most type 2 families have missense mutations, whereas most type 1 families are affected by deletions or premature termination mutations. Prognostic counseling regarding the lifetime risk of pheochromocytoma can be aided by determination of the underlying mutation in patients without family histories of VHL.