Sietske N. Heyn is a medical writer with a PhD in neuroscience. Dr. Heyn's education includes a BS with honors from the University of Oregon, and a doctoral degree in neuroscience from the University of California at Davis. After completing postdoctoral training at the University of California, San Francisco, and many years of working as a medical writer at the Stanford University Center for Down Syndrome Research, Dr. Heyn now runs her own medical writing business.
Dr. Perlstein received his Medical Degree from the University of Cincinnati and then completed his internship and residency in pediatrics at The New York Hospital, Cornell medical Center in New York City. After serving an additional year as Chief Pediatric Resident, he worked as a private practitioner and then was appointed Director of Ambulatory Pediatrics at St. Barnabas Hospital in the Bronx.
Exactly how the extra genes from chromosome 21 lead to Down syndrome is still
not clear. Scientists believe that the increased presence of specific genes
alters the interaction between these and other genes. Some genes will become
more active and others less active than normal, leading to changes in the
development and maintenance of the body. Why some individuals are more severely
affected than others might have to do with how many and which specific extra
genes were inherited.
Scientists are trying to find out which genes from chromosome 21, when present
in three copies, are responsible for the different characteristics of Down
syndrome. Currently, about 400 genes on chromosome 21 have been identified, but
the functions of most are still unknown. Through human studies and animal
models, scientists are making progress in understanding the functions of
individual genes.
What are the risk factors for conceiving a child with Down syndrome?
The only well known risk factor for conceiving a child with Down syndrome is
advanced maternal age. The older the woman is at conception, the greater the
risk of having a child with Down syndrome.
Mother's age at conception Risk of Down syndrome
25 years 1 in 1,250
30 years 1 in 1,000
35 years 1 in 400
40 years 1 in 100
45 years 1 in 30
Parents who have conceived a child with Down syndrome have a 1% increased
risk of conceiving another child with Down syndrome. If a parent is a carrier of
a chromosome 21 translocation, the risk can be as high as 100%.
Women with Down syndrome have a 50% risk of conceiving a child with Down
syndrome. If the father has Down syndrome, the risk of conceiving a child with
Down syndrome is also increased.
Leukemia is a type of cancer of the blood cells in which the growth and development of the blood cells are abnormal. Strictly speaking, leukemia should refer only to cancer of the white blood cells (the leukocytes) but in practice it can apply to malignancy of any cellular element in the blood or bone marrow, as in red cell leukemia (erythroleukemia).
Dementia is a significant loss of intellectual abilities such as memory capacity, severe enough to interfere with social or occupational functioning. There are different criteria classification schemes for dementias such as cortical, subcortical, progressive, primary, and secondary dementias. Other conditions and medication reactions can also cause dementia. Dementia is diagnosed based on a certain set of criteria. Treatment for dementia is generally focused on the symptoms of the disease.
The Eustachian tube is a membrane lined tube that connects the middle ear space to the back of the nose. Problems include partial or complete blockage which can cause popping, clicking, and ear fullness. Allergies, sinus and ear infections, or the common cold can cause this blockage, while altitude changes can cause symptoms in those persons with Eustachian tube problems. Treatment includes several maneuvers (swallowing, chewing gum, yawning etc.), which can be done to improve Eustachian tube function.
Turner syndrome is an inherited chromosomal condition affecting women. Women with Turner syndrome do not have ovarian function, and features of the syndrome include webbed neck, lymphedema of the hands and feet, heart defects, kidney problems, and skeletal abnormalities. The X chromosome is related to Turner syndrome. Treatment focuses on the symptoms of the syndrome.
Fragile X syndrome is the most common inherited form of mental retardation. It's caused by a mutation on the X chromosome. People with Fragile X syndrome suffer from physical, social, emotional, speech, language, sensory, intelligence, and learning impairments. There is no definitive treatment for Fragile X, though there are ways to minimize the symptoms.
Klinefelter syndrome, also referred to as XXY condition, is a genetic disease. Klinefelter syndrome affects mostly males. Symptoms include decreased testosterone levels, development of breasts, wider hips, and infertility. Some men with Klinefelter syndrome have no symptoms. Treatment includes educational, therapeutic, and medical therapy.
Genetic disease is a disorder or condition caused by abnormalities in a person's genome. Types of genetic inheritance include single inheritance (for example, cystic fibrosis, sickle cell anemia, Marfan syndrome, and hemochromatosis), multifactoral inheritance, chromosome abnormalities (for example, Turner syndrome, and Klinefelter syndrome), and mitochondrial inheritance (for example, epilepsy and dementia).
Hirschsprung's disease (Hirschsprung), is a disease of the nerve cells of of the large intestine. The primary symptom of Hirschsprung's disease is constipation. Hirschsprung's disease is diagnosed through barium enema, and treatment is surgery.
Pregnancy planning is important to help prevent exposure of the mother and fetus to potentially harmful medications and substances during the early days, and throughout the pregnancy. Nutritional planning, prevention of birth defects, conditions such as high blood pressure, heart disease, diabetes, and kidney disease need careful monitoring. Gestational diabetes, preeclampsia, and pregnancy induced hypertension are conditions that may arise during pregnancy. Immunizations, inherited disorders, exercise, air travel, intercourse, and birth control are important factors to consider when planning a pregnancy.
Spina bifida is the most common neural tube defect in the United States. There are four types of spina bifida; 1) occulta, 2) closed neural tube defects, 3) meningocele, and 4) myelomeningocele. The cause of spina bifida is not known. Theories include genetic, nutritional, and environmental factors. Lack of folic acid during pregnancy is highly suspected. Symptoms of spina bifida vary from individual to individual. Treatment depends on the type of spina bifida the person suffers.
Microcephaly is a genetic condition where the circumference of the head is smaller than normal due to underdeveloped brain. Microcephaly is caused by genetic abnormalities, or from abuse of alcohol, drugs, infection (for example, German measles or chickenpox), exposure to toxins, or PKU while the mother is pregnant. Symptoms of microcephaly depend upon the severity of the accompanying syndrome. There is not treatment for microcephaly.
Noonan syndrome is a genetic disorder that causes birth defects (congenital malformations) such as short stature, caved-in chestbone, webbing of the neck as well as heart and blood vessel defects. Named after Dr. Jacqueline A. Noonan it is inherited as an autosomal dominant disorder. The Noonan gene (NS1) is on a nonsex (autosomal) chromosome (number 12) and is transmitted from a parent with a 50% probability to boy or girl. Treatment for Noonan syndrome is directed toward the problems that may occur in a given affected individual. The heart defects may require surgical treatment. The expected outcome (prognosis) depends on the extent and severity of the features that are present.
Your health care provider may refer you to a genetic professional. Universities and medical centers also often have affiliated genetic professionals, or can provide referrals to a genetic professional or genetics clinic. Genetic counseling provides patients and family members the tools to make the right choice in regard to test for a disease or condition.
Kids Health RSS
Healthy Living Tips
This site complies with the