When Turcot syndrome demonstrates an autosomal dominant inheritance pattern, it means an affected parent has a 50% chance of passing on the mutated gene (the disease) to their children. When Turcot syndrome demonstrates an autosomal recessive inheritance pattern, it means two mutated genes, one from each parent has been passed on to the affected individual. Two carrier parents have a 50 % chance of having an unaffected child who also is a carrier, and a 25% chance of having an affected child with two recessive genes.
Turcot syndrome is characterized by colonic polyp growth that occur in association with a primary brain tumor.
Patients with Turcot syndrome have an increased risk of developing colorectal cancer. The colonic growths associated in Turcot syndrome can cause bleeding from the rectum, diarrhea, constipation, abdominal pain, and/or weight loss.
Patients with Turcot syndrome have an increased risk of developing brain cancer, commonly in the form of glioblastoma multiforme (GBM) or a medulloblastoma.
Turcot syndrome may be associated with Lynch syndrome, or hereditary nonpolyposis colorectal cancer (HNPCC). This is a hereditary cancer syndrome resulting from defective DNA mismatch repair genes, causing a predisposition to cancer growth via microsatellite instability.
Patients with Turcot syndrome who display an association with or additional diagnosis of Lynch syndrome commonly also have a glioma. GBM is the most common malignant tumor of glial cells in the brain and is derived from astrocytes.
Turcot syndrome may be associated with familial adenomatous polyposis (FAP). FAP is an autosomal dominant disorder that results from a mutation in the adenomatous polyposis coli (APC) gene on chromosome 5 that also undergoes a “second hit” or “two-hit” deletion of the other allele, resulting in higher prevalence of colonic polyp development and associated colorectal carcinoma (CRC).
The type of brain cancer that a patient with Turcot syndrome develops when associated with FAP is a medulloblastoma. Medulloblastomas are considered one of the most common primary central nervous system (CNS) tumors in children. They tend to occur in the cerebellum and can present with multiple signs and symptoms including hydrocephalus and truncal ataxia.
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