Common Chromosomal and Genetic Disorders in Children

Down Syndrome

Incidence

1 per 700-1,000 births

Characteristics^a

Children with Down syndrome have one extra chromosome. Physical characteristics include a protruding tongue, thick lips, flat nose, short neck, wide gaps between toes, short fingers, specific health problems, and risks for heart problems and hearing loss. Mental retardation can range from mild to severe. Children often have good visual discrimination skills and may be better at understanding verbal language than producing it.

Implications for Care

Provide explicit instruction in any delayed skills (e.g., in language). Address health issues such as heart problems and potential feeding difficulties.

Klinefelter Syndrome

Incidence

1 per 500-1,000 boys

Characteristics^a

Only boys have Klinefelter syndrome; they have one Y chromosome and two X chromosomes. Diagnosis may not occur until adolescence, when testes fail to enlarge. Affected boys tend to have long legs, to grow modest breast tissue, a/1d to remain sterile. They tend to show lower than average verbal ability and some speech and language delays.

Implications for Care

Offer an enriched verbal environment. Medical treatment may be given to support development of male sexual characteristics.

Turner Syndrome

Incidence

1 per 2,500-5,000 girls

Characteristics^a

Only girls have Turner syndrome; they have one X chromosome and are missing the second sex chromosome. Affected girls have broad chests, webbed necks, short stature, and specific health problems. They do not show normal sexual development. They may show normal verbal ability but lower than average ability in processing visual and spatial information.

Implications for Care

Provide instruction and support related to visual and spatial processing. Hormone therapy helps with bone growth and development of female characteristics.

Prader-Willi Syndrome

Incidence

1 per 10,000-25,000 births

Characteristics^a

A deletion from a gene segment on chromosome 15 is inherited from the father. Children with this syndrome tend to become obese and show mental retardation; they also have small hands and feet and are short in stature. They may develop maladaptive behaviors such as throwing frequent temper tantrums and picking at their own skin. Beginning at ages 1-6, children may eat excessively, hoard food, and eat unappealing substances.

Implications for Care

Create developmentally appropriate plans to help children regulate eating, decrease inappropriate behaviors, and increase acceptable emotional expression. Seek medical care as necessary.

Angelman Syndrome

Incidence

1 per 10,000-30,000 births

Characteristics^a

A deletion from a gene segment on chromosome 1 5 is inherited from the mother. Children with this syndrome show mental retardation, a small head, seizures, and jerky movements. They have unusual, recurrent bouts of laughter not associated with happiness.

Implications for Care

Provide appropriate educational support suited to children's skills and developmental levels. Seek medical care as necessary.

Single-Gene Defects

Children with single-gene defects have a problem on a dominant gene (an error on one of the 22 paired chromosomes, that is, on any chromosome except X or Y^b), a recessive defect on both chromosomes in One of the 22 matched pairs, or a problem in a recessive gene on the X chromosome (boys) or a problem in a gene on both X chromosomes (girls).

Neurofibromatosis

Incidence

Mild form occurs in 1 per 2,500-4,000 births; severe form occurs in 1 per 40,000-50,000 births

Characteristics^a

Children with this dominant-gene defect develop benign and malignant tumors in the central nervous system. The condition may be caused by an error in a gene that would normally suppress tumor growth. Learning disabilities are somewhat common and mental retardation occurs occasionally. Most individuals experience only minor symptoms, such as having colored and elevated spots on their skin.

Implications for Care

Address learning disabilities; offer adaptive services to children with mental retardation. Tumors may need to be removed or treated. Surgery or braces may be needed if the spine becomes twisted.

Huntington Disease (HD)

Incidence

3 to 7 per 100,000 births

Characteristics^a

Children with this dominant-gene defect develop a progressive disorder of the central nervous system. Signs typically appear by age 35 to 45, though age of first symptoms has varied between 2 and 85 years. HD may be caused by the production of a protein that destroys brain cells. Early signs include irritability, clumsiness, depression, and forgetfulness. Eventually, loss of control over movements of arms, legs, torso, or facial muscles occurs, speech becomes slurred, and severe mental disturbances arise.

Implications for Care

Remove sharp edges from the physical environment. When memory deteriorates, provide visual instructions about daily tasks. Medication may be given to alleviate movement problems and depression.

Phenylketonuria (PKU)

Incidence

1 per 15,000 births, with rates highest in people of Celtic origin (e.g., from Ireland and Scotland)

Characteristics^a

Children with this recessive-gene defect are at risk for developing mental retardation, eczema, seizures, and motor and behavioral problems such as aggression, self-mutilation, and impulsiveness. When children have both recessive genes for PKU, their livers cannot produce an enzyme that breaks down phenylalanine (an amino acid); this substance accumulates and becomes toxic to the brain.

Implications for Care

Provide educational materials to enhance planning and memory skills and compensate for limitations. When phenylalanine is restricted from diet, children develop much more normally, and mental retardation is avoided. Subtle problems may still result (e.g., awkward pencil grip and learning disabilities).

Sickle Cell Disease

Incidence

1 per 500-600 children of African (Black) descent; rates are also elevated in people of Mediterranean descent

Characteristics^a

Children with this recessive-gene defect develop problems with blood circulation. The disease causes red blood cells to grow rigid, and passage of blood through small vessels causes pain. Children may experience many serious conditions, including stroke, infection, tissue damage, and fatigue. Symptoms become obvious during the first or second year of life.

Implications for Care

Be alert to medical crises, such as strokes. Offer comfort to children who are tired or in pain. Treatments include blood transfusions, medication for pain and infections, and other medicines to reduce frequency of medical crises.

Cystic Fibrosis (CF)

Incidence

1 per 3,300 children from European American backgrounds and 1 per 9,500 children from Hispanic American backgrounds

Characteristics^a

Children with this recessive-gene defect have glands that produce large amounts of abnormally thick, sticky mucus, which creates serious problems for breathing and digestion. CF is usually noticed in infancy due to persistent coughing, wheezing, pneumonia, and big appetite with little weight gain. Many individuals with CF now live well into their 40s.

Implications for Care

Be aware of symptoms that require medical care. The condition is often treated with physical therapy, medication, and bronchial drainage.

Tay-Sachs Disease

Incidence

1 per 2,500-3,600 children among Ashkenazi Jews (of Eastern European ancestry)

Characteristics^a

Children with this recessive-gene defect develop a fatal, degenerative condition of the central nervous system. They lack an enzyme required to break down a fatty substance in brain cells. At about 6 months of age, children slow down in development, lose vision, display an abnormal startle response, and go into convulsions. Other functions are gradually lost, and children become mentally retarded, cannot move, and die by age 3 or 4.

Implications for Care

Offer love and attention as you would to other children. Be alert to new accommodations that may be needed in the environment, such as stabilizing and securing the surroundings when children lose sight. There is no known cure or treatment.

Thalassemia (Cooley's Anemia)

Incidence

1 in 800-2,500 individuals of Greek or Italian descent in the U.S.; rates are lower in other groups

Characteristics^a

Children with this recessive-gene defect develop a disease of blood cells in which oxygen is not transmitted effectively. They become pale, fatigued, and irritable within their first 2 years of life. Individuals with serious forms of the condition may develop feeding problems, diarrhea, and enlargement of the spleen and heart, infections, and unusual facial features and bone structures. Young people severely impaired by this condition sometimes die by early adulthood.

Implications for Care

Help children to cope with their health problems. Treatment may include blood transfusions, antibiotics, and occasionally bone marrow transplants.

Duchenne Muscular Dystrophy

Incidence

1 per 3,000 to 4,000 boys

Characteristics^a

Only boys acquire this X-linked recessive-gene defect, which causes a progressive muscular weakness because of a gene's failure to produce an essential protein needed by muscle cells. Between ages 2 and 5, affected boys begin to stumble and walk on their toes or with another unusual gait. They may lose the ability to walk between ages 8 and 14 and may later die from respiratory and cardiac problems.

Implications for Care

Watch for respiratory infections and heart problems. Treatments include physical therapy, orthopedic devices, surgery, and medications to reduce muscle stiffness.

Notes

^aThis table describes typical symptoms for children with particular chromosomal and genetic problems. Children's actual level of functioning depends on the medical treatments they receive; their experiences with families, teachers, other caregivers, and other children; and their health and other genes they might possess. New medical treatments and educational interventions are constantly being tested, and many will increase quality of life for these children.

^bX-linked dominant defects also occur but are rare. For example, children who receive the gene for Hypophosphatemia on the X chromosome produce low levels of phosphate and. a result, have soft bones that are easily deformed.

Sources: Blachford, 2002; Burns et al., 2000; Cody & Kamphaus, 1999; Dykens & Cassidy, 1999; Massimini, 2000; K. L. Moore & Persaud, 2003; Nilsson & Bradford, 1999; M. P. ""I & Schulte, 1999; J. T. Smith, 1999; Waisbren, 1999; Wynbrandt & Ludman, 2000.