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.
Characteristic Features and Symptoms of Down Syndrome
Although the severity of Down syndrome ranges from mild to severe, most
individuals with Down syndrome have widely recognizable physical
characteristics. These include:
a flattened face and nose, a short neck, a small mouth sometimes with a
large, protruding tongue, small ears, upward slanting eyes that may have
small skin folds at the inner corner (epicanthal fold);
white
spots (also known as Brushfield spots) may be present on the colored part of the
eye (iris);
the hands are short and broad with short fingers, and with a single
crease in the palm;
poor muscle tone and loose ligaments are also common; and
development and growth is usually delayed and often average height and
developmental milestones are not reached.
What is Down syndrome?
Down syndrome (also called Trisomy 21) is a genetic disorder that occurs in
approximately 1 of 800 live births. It is the leading cause of cognitive
impairment. Down syndrome is associated with
mild to moderate learning
disabilities, developmental delays, characteristic facial features, and low
muscle tone in early infancy. Many individuals with Down syndrome also have
heart defects, leukemia, early-onset
Alzheimer's disease, gastro-intestinal
problems, and other health issues. The symptoms of Down syndrome range from mild
to severe.
Life expectancy for individuals with Down syndrome has dramatically increased
over the past few decades as medical care and social inclusion have improved. A
person with Down syndrome in good health will on average live to age 55 or
beyond.
Down syndrome is named after Doctor Langdon Down, who in 1866 first described
the syndrome as a disorder. Although Doctor Down made some important
observations about Down syndrome, he did not correctly identify what causes the
disorder. It wasn't until 1959 that scientists discovered the genetic origin of
Down syndrome.
What are the chromosome basics of Down syndrome?
Genes on an extra copy of chromosome 21 are responsible for all
characteristics associated with Down syndrome. Normally, each human cell
contains 23 pairs of different chromosomes. Each chromosome carries genes, which
are needed for proper development and maintenance of our bodies. At conception,
an individual inherits 23 chromosomes from the mother (through the egg cell) and
23 chromosomes from the father (through the sperm cell).
However, sometimes a person inherits an extra chromosome from one of the
parents. In Down syndrome, an individual most often inherits two copies of
chromosome 21 from the mother and one chromosome 21 from the father for a total
of three chromosomes 21. Because Down syndrome is caused by the inheritance of
three chromosomes 21, the disorder is also called trisomy 21. About 95% of
individuals with Down syndrome inherit an entire extra chromosome 21.
Approximately 3% to 4% of individuals with Down syndrome do not inherit an
entire extra chromosome 21, but just some extra chromosome 21 genes, which are
attached to another chromosome (usually chromosome 14). This is called a
translocation. Most of the time, translocations are random events during
conception. In some instances however, a parent is a balanced carrier of a
translocation: The parent has exactly two copies of chromosome 21, but some of
the genes are distributed to another chromosome. If a baby inherits the
chromosome with the extra genes from chromosome 21, then the child will have
Down syndrome (two chromosomes 21 plus extra chromosome 21 genes attached to
another chromosome).
About 2% to 4% of people with Down syndrome inherit additional genes from
chromosome 21, but not in every cell of the body. This is known as mosaic Down
syndrome. These individuals may, for example, have inherited extra genes from
chromosome 21 in their muscle cells, but not in any other type of cell. Because
the percentage of cells with extra genes from chromosome 21 varies in people
with mosaic Down syndrome, they often don't have all the typical physical
characteristics and may not be as severely intellectually impaired as people
with full trisomy 21. Sometimes, mosaic Down syndrome is so mild that it will go
undetected. On the other hand, mosaic Down syndrome can also be misdiagnosed as
trisomy 21, if no genetic testing has been done.
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.
What are genetic professionals and what do they do?
Genetics professionals are health care professionals with specialized degrees
and experience in medical genetics and counseling. Genetics professionals
include geneticists, genetic counselors and genetics nurses.
What is genetic counseling and evaluation?
Genetic professionals work as members of health care teams providing
information and support to individuals or families who have genetic disorders or
may be at risk for inherited conditions. Genetic professionals:
Assess the risk of a genetic disorder by researching a family's history and
evaluating medical records.
Weigh the medical, social and ethical decisions surrounding genetic
testing.
Provide support and information to help a person make a decision about
testing.
Interpret the results of genetic tests and medical data.
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