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Common Chromosomal and Genetic Disorders in Children (page 2)

By — Pearson Allyn Bacon Prentice Hall
Updated on Jul 24, 2013

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 Yb), 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

Characteristicsa

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

Characteristicsa

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)

Characteristicsa

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

Characteristicsa

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.

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