Gerstmann-Straussler-Scheinker disease is a progressively disabling and ultimately fatal brain infection caused by a unique protein particle called a prion. Gerstmann-Straussler-Scheinker disease is an inherited disorder, and occurs in familial clusters.
Gerstmann-Straussler-Scheinker disease belongs to a group of diseases originally known as slow virus infections. Currently, slow virus infections are classed together as transmissible spongiform encephalopathies (TSE), or prion diseases . Other TSEs include kuru , Creutzfeldt-Jakob disease , and fatal familial insomnia. The TSE called new variant Creutzfeldt-Jakob disease (also known colloquially as "Mad Cow Disease") has received a great deal of public attention. The TSEs, including Gerstmann-Straussler-Scheinker disease, involve abnormal clumps of protein that accumulate throughout the brain, destroying brain tissue and leaving spongy holes.
About 10% of all transmissible spongiform encephalopathies are inherited. Gerstmann-Straussler-Scheinker disease occurs worldwide, but because of its pattern of familial transmission, cases tend to occur in specific geographic clusters. Only a few families have been identified as carrying the mutation that causes Gerstmann-Straussler-Scheinker disease.
Gerstmann-Straussler-Scheinker disease is caused by a genetic mutation caused by an infectious protein particle called a prion, which stands for proteinaceous infectious particle. A prion is similar to a virus, except that it lacks any nucleic acid, which prevents it from reproducing. Prions are abnormal versions of proteins that are found in the membranes of normal cells. These abnormal proteins can be passed directly to individuals through the ingestion of prion-infected tissue or when open sores on the recipient's skin are exposed to prion-infected tissue. In addition to being transmissible (as are other infectious agents like viruses or bacteria), prions are unique because they can also be acquired through genetic inheritance. This is the case with Gerstmann-Straussler-Scheinker disease.
In Gerstmann-Straussler-Scheinker disease, one of several possible specific gene mutations is present, leading to the abnormal deposition of tangled masses of a protein called amyloid throughout the brain. The spin-ocerebellar tracts (nerves that run from the brain's cerebellum throughout the spinal cord) become increasingly atrophied (shrunken) and dysfunctional over time.
Symptoms of Gerstmann-Straussler-Scheinker disease tend to begin in later middle age, usually between the ages of 40 and 55. Early symptoms include unsteady gait and difficulty walking, discoordination, clumsiness. As the disease progresses, the individual experiences difficulty speaking; abnormal, involuntary, rapid darting eye movements; paralyzed eye movement; deafness; blindness; and dementia . Death often occurs within five to 10 years of the initial symptoms.
Diagnosis of Gerstmann-Straussler-Scheinker disease is arrived at through characteristic abnormalities found on the electroencephalogram (EEG), a test of brain waves and electricity. MRI studies and biopsies (tissue samples) from the brain may also show changes that are characteristic of prion disease. Like certain forms of CJD, Gerstmann-Straussler-Scheinker disease can be analyzed with DNA testing; specifically, the white blood cells are examined in order to identify one of the mutations associated with the disease.
Diagnosis of slow virus infection is usually made by a neurologist .
There are no available treatments for Gerstmann-Straussler-Scheinker disease. It is relentlessly progressive, incurable, and fatal. Supportive care for the patient and his or her family is the only treatment.
Gerstmann-Straussler-Scheinker disease is always fatal.
Gerstmann-Straussler-Scheinker disease is unique among transmissible spongiform encephalopathies, because mutations can be identified through DNA analysis of a sufferer's white blood cells. This allows other family members to be counseled regarding their personal risk of disease inheritance, projected age of disease onset, and potential illness duration. While some mutations sentence an individual to certain disease, other locations of mutations have only a 50% chance of leading to actual disease. Additionally, in families known to carry a mutation of Gerstmann-Straussler-Scheinker disease, amniocentesis can identify fetuses affected by the mutation, allowing families to make decisions about whether or not to continue a pregnancy.
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Rosalyn Carson-Dewitt, MD