This paper provides a comprehensive overview of Huntington's disease (HD), a hereditary brain disorder affecting approximately 30,000 Americans. The paper examines HD's autosomal dominant inheritance pattern, explaining why each child of an affected parent faces a 50% chance of inheriting the defective gene. It discusses the disease's gradual onset—typically between ages 35 and 55—and its progressive deterioration of motor, cognitive, and emotional function over 10 to 30 years. The paper also explores the broader impact HD has on families and caregivers, and concludes with a discussion of gene silencing, a promising emerging treatment that targets the mutant huntingtin gene while leaving the healthy copy intact.
Although it was once considered a rare disease, Huntington's disease (HD) is now recognized as one of several frequently encountered hereditary disorders. It is estimated that 30,000 people in the United States have the disease. People affected by HD require extensive care from their families and loved ones, and because of this need, the condition affects a wide circle of people close to those who are ill ("Huntington's Disease"). This widespread impact on so many lives is one reason that promoting HD awareness is so important.
HD is an inherited brain disorder that leads to loss of physical control and mental capacity. Caused by an inherited defect in a single gene, HD is an autosomal dominant disorder, which means that a person needs only one copy of the defective gene to develop the disorder. With the exception of genes on the sex chromosomes, a person inherits two copies of every gene — one from each parent. A parent with a defective Huntington gene could pass along either the defective copy or the healthy copy. Therefore, each child in a family has a 50% chance of inheriting the gene that causes the disorder (Mayo Clinic Staff).
Given that the majority of people develop the disease between the ages of 35 and 55, those who are aware of their genetic risk face an additional dilemma: Should they be tested to see if they carry the gene? Should they start a family?
Huntington's disease affects approximately 1 person in 10,000, but its genetic nature means that it affects a significant number of family members as well. Approximately 200,000 Americans are at risk of inheriting the disease from an affected parent. Every person who inherits the HD gene will eventually develop the disease if they do not die of other causes first. Even though HD does not affect large numbers of people in absolute terms, a patient with HD is affected for a very long period of time — typically 10 to 30 years. For all of these reasons, HD represents a significant public health challenge (Quarrell).
The HD genetic defect causes nerve cell loss in the brain. Symptoms may develop gradually and will affect an individual's ability to move, think, and process thoughts and feelings. After the onset of HD, a person's functional abilities deteriorate progressively over time, with the rate and course of the disease varying from individual to individual. From onset of the disease to death is a period of approximately 10 to 30 years (Mayo Clinic Staff).
As described by the Mayo Clinic, the disease's progression follows a recognizable pattern of increasing disability across motor, cognitive, and psychiatric domains, though the precise timeline differs for each patient.
"Late-stage care needs and causes of death"
"Gene silencing targets mutant huntingtin gene safely"
Researchers try to avoid making projections regarding how soon a treatment will become available, but they are so encouraged by advances in gene silencing that the Huntington's Disease Society of America anticipates the first human trial starting within the next two years (Orth). Their progress represents an encouraging development in the fight to end a disease that has such devastating and far-reaching effects.
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