von Hippel-Lindau (VHL) disease (MIM 193300) is a dominantly inherited familial cancer syndrome. It is caused by mutations in the VHL tumor suppressor gene with an incidence of
1:31-36000 live births worldwide across all ethnic backgrounds, with similar prevalence in both genders (Maher et al., 1991; Maher, et al.2004). The prevalence however was shown to be higher in some population withtin the same ethnicity such as 1:39 000 in South-West Germany and 1:53 000 in Eastern England (Maher ER et al, 1991; Neumann H et al, 1991). VHL is characterized by marked age-dependent penetrance and phenotypic variability. The factors that affect the actual clinical expression and tumor formation, including age of onset, tissue and organ-specific lesions, severity of lesions, and recurrence, are unknown. VHL main clinical manifestations are:
Hemangioplastoms of the central nervous system (CNS) which are typically located in the cerebellum, but can also occur at the brainstem, spinal cord, and rarely, at the lumbosacral nerve roots and supratentorial (Neumann et al., 1995). Retinal or CNS hemangioblastomas are often the earliest manifestations of VHL disease and the most common, occurring in up to 80% of patients (Maher et al., 1990b; Melmon and Rosen, 1964; Weil et al., 2003). VHL-associated cerebellar hemangioblastomas are diagnosed at a mean age of 29-33 years, much earlier than sporadic cerebellar hemangioblastomas (Hes et al., 2000a, 2000b; Wanebo et al., 2003). These lesions are rarely malignant, but enlargement or bleeding within the CNS can result in neurological damage and death (Pavesi et al., 2008). A lower incidence of CNS hemangioblastomas has been documented in specific ethnic populations (12% Finland (Niemela M et al., 1999); 5% German (Zbar B et al., 1999). Patients with cerebellar haemangioblastomas typically present with symptoms of increased intracranial pressure and limb or truncal ataxia (depending on the precise location of the tumor). Wanebo et al. (2003) showed most CNS hemangioblastomas were associated with cysts that were often larger than other hemangioblastomas.
Pheochromocytomas are endocrine neoplasias with intra- or extra-adrenal gland lesions that appear histologically as an expansion of large chromaffin positive cells, derived from neural crest cells (Lee et al., 2005). Seven to 18% of VHL patients are afflicted with pheochromocytomas (Crossey et al., 1994a; Garcia et al., 1997). The absence or present of this phenotype will type the VHL into type 1or 2 (A,B,C), respectively (Woodward ER et al., 1997; Hofstra RMW et al., 1996). Untreated pheochromocytomas can result in hypertension and subsequent acute heart disease, brain edema, and stroke.
4.3. Clear cell renal cell carcinoma (RCC)
Clear cell renal cell carcinoma (RCC) occurs in up to 70% of patients with VHL and is a frequent cause of death. 70% of VHL patients have the risk of developing RCC by 60 years old (Maher et al., 1990b, 1991; Whaley et al., 1994), at an average age of 44 years versus the average age of 62 years, at which sporadic RCC develops in the general population (http://www.umd.be/VHL/W_VHL /clinic. shtml). Renal cysts are common in VHL patients as well; however, unlike the completely benign cysts in the general population, renal cysts in VHL patients might degenerate into RCC (Kaelin et al., 2004). However, it is unlikely that RCC in all VHL patients originates from cysts, or that all cysts will eventually become malignant. RCC often overproduces VEGF, and thus can be very vascular (Berse et al., 1992; Sato et al., 1994; Takahashi et al., 1994).
VHL patient can also have low-grade adenocarcinomas of the temporal bone, also known as endolymphatic sac tumors (ELST), pancreatic tumor, and epididymal or board ligament cystadenomas (Gruber et al., 1980; Neumann and Wiestler, 1991; Maher et al., 2004; Kaelin et al., 2007). ELST in VHL cases can be detected by MRI or CT imaging in up to 11% of patients (Manski TJ, et al., 1997). Although often asymptomatic, the most frequent clinical presentation is hearing loss (mean age 22 years), but tinnitus and vertigo also occur in many cases. In addition to the inherited risk for developing cancer, VHL patients develop cystic disease in various organs including the kidney, pancreas, and liver (Hough et al., 1994; Lubensky et al., 1998; Maher et al., 1990b; Maher, 2004).
Tumor growth commonly cycled between growth and quiescent phases. Patients with numerous tumors experienced growth and quiescent phases simultaneously, suggesting that a combination of acquired genetic lesions and hormonal activity influence tumor growth.
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