Von Hippel-Lindau disease
Also Known As: Von Hippel-Lindau disease, VHL
Von Hippelâ€“Lindau (VHL) is a rare, autosomal dominant genetic condition in which hemangioblastomas are found in the cerebellum, spinal cord, kidney and retina. These are associated with several pathologies including renal angioma, renal cell carcinoma (clear cell variety) and pheochromocytoma. VHL results from a mutation in the von Hippelâ€“Lindau tumor suppressor gene on chromosome 3p25.3.
Signs and symptoms associated with VHL include headaches, problems with balance and walking, dizziness, weakness of the limbs, vision problems, and high blood pressure. Conditions associated with VHL include angiomatosis, hemangioblastomas, pheochromocytoma, renal cell carcinoma, pancreatic cysts (pancreatic serous cystadenoma) and café au lait spots. Angiomatosis occurs in 37.2% of patients presenting with VHL and usually occurs in the retina. As a result, loss of vision is very common. However, other organs can be affected: strokes, heart attacks, and cardiovascular disease are common additional symptoms.
As long as one copy of the VHL gene is producing functional VHL protein in each cell, tumors do not form. Since both alleles need to be mutated in order for the disorder to develop, the second allele must develop the mutation in at least one other cell in their bodies. This is known as the two-hit hypothesis. If a mutation occurs in the second copy of the VHL gene, the cell will have no working copies of the gene and will produce no functional VHL protein. A lack of this protein allows tumors characteristic of von Hippel–Lindau syndrome to develop.
An inherited mutation of the VHL gene is responsible for about 80 percent of cases. In about 20 percent of cases, however, the altered gene is the result of a new mutation that occurred during the formation of reproductive cells (eggs or sperm) or early in fetal development. This is quite rare because the probability of a mutation occurring in a cell where both alleles are previously normal is quite small. Whether by new mutation or inherited mutation, the aforementioned second hit still needs to occur in order for a tumor to appear.
There is a wide variation in the age of onset of the disease, the organ system affected and the severity of effect. This suggests that the second mutation can occur in different types of cells and at various times of a person's life.