Dysplasia is a combination of two Greek words; dys-, which means difficult or disordered; and plassein, to form. In other words, dysplasia is the abnormal or disordered organization of cells into tissues. All abnormalities relating to abnormal tissue formation are classified as dysplasias.
Description
Tissues displaying abnormal cellular organization are called dysplastic. Dysplasias may occur as the result of any number of stimuli. Additionally dysplasia may occur as a localized or a generalized abnormality. In a localized dysplasia, the tissue abnormality is confined to the tissue in a single area, or body part. In a generalized dysplasia, the abnormal tissue is an original defect leading to structural consequences in different body parts.
Localized dysplasia
Localized dysplasia may occur as the result of any number of stimuli and affect virtually any organ. Stimuli leading to localized dysplasia may include viruses, chemicals, mechanical irritation, fire, or even sunlight. Sunburned skin, for example, is dysplastic. The dysplasia caused from sunburn, however, corrects itself as the sunburned skin heals.
Any source of irritation causing inflammation of an area will result in temporary dysplasia. Generally, when the source of irritation is removed the dysplasia will correct itself. Removing the irritant generally allows cell structure and organization to return to normal in a localized dysplasia.
Unfortunately, dysplasia can become permanent. This can occur when a source of irritation to a given area cannot be found and removed, or for completely unknown reasons. A continually worsening area of dysplasia can develop into an area of malignancy (cancer). Tendencies toward dysplasia can be genetic. They may also result from exposure to irritants or toxins, such as cigarette smoke, viruses, or chemicals.
The Pap smear, a medical procedure commonly performed on women, is a test for dysplasia of a woman's cervix. The cervix is the opening to a woman's uterus that extends into the vagina. It is a common area where cancers may develop. A Pap smear involves sampling the outer cells of a woman's cervix to look for microscopic cellular changes indicative of dysplasia, or abnormal tissue changes. Less than five percent of Pap smears indicate cervical dysplasia. Cervical dysplasia is most common in women who are 25–35 years old.
The degree of dysplasia present in cervical cells can be used as an indicator for progression to a cancerous condition. Early treatment of cervical dysplasia is very effective in halting progression of the dysplasia to cancer. Essentially, all sexual risk factors correlate with dysplasia. Exposure to the AIDS virus (HIV) or certain strains of human papilloma virus (HPV) raises a woman's risk to develop cervical dysplasia. Increased risk is also linked to having unprotected sex at an early age, having unprotected sex with many partners, or becoming pregnant before age 20. Smoking increases a woman's risk to develop cervical dysplasia. Prenatal exposure to diethylstilbestrol (DES), a hormonal drug prescribed from 1940 to 1971 to reduce miscarriages, also increases a woman's risk for cervical dysplasia. Exactly how these risk factors are connected to cervical dysplasia is not well understood.
become sexually active, whichever occurs earlier. If a woman has had three negative annual Pap tests in a row, this test may be done less often at the judgment of a woman's health care provider.
Generalized dysplasia
A generalized dysplasia often presents as multiple malformations in a variety of structures. Any structural consequences are due to the particular tissue organization defect and the spectrum of organs that utilize the dysplastic tissue. Generalized dysplasias are often genetic. They may be inherited or occur due to a new genetic change in an individual. The structural problems associated with generalized dysplasias usually begin during embryonic development.
This type of dysplasia is classified according to the specific tissue affected. Generalized dysplasias account for some important groups of inherited disorders including the skeletal dysplasias and ectodermal dysplasias.
SKELETAL DYSPLASIAS Skeletal dysplasias affect the growth, organization, and development of the bony skeleton. These conditions are always genetic. The effects of skeletal dysplasias vary. A mild skeletal dysplasia may cause someone to be of shortened height without any other complication. Other skeletal dysplasias may severely reduce height, causing dwarfism with disproportion and other bone deformity. The most severe
skeletal dysplasias are incompatible with life, causing babies to die before or soon after birth.
Achondroplasia is a common, highly recognizable skeletal dysplasia. This disorder occurs in approximately one in 20,000 live births. Achondroplasia affects bone growth resulting in short stature, a large head, characteristicfacial features, and disproportionately short arms and legs. This disorder is caused by a mutation in a single gene called fibroblast growth gactor receptor three (FGFR3). Achondroplasia may be inherited like most generalized dysplasias, but more commonly it occurs due to a new mutation in a family. Over 80% of cases of achondroplasia are sporadic, or due to new mutations. The appearance of new mutations for achondroplasia is more frequently observed in children born to older fathers.
Hypochondroplasia is a common, milder skeletal dysplasia caused by different mutations in the gene responsible for achondroplasia, the FGFR3 gene. People with hypochondroplasia display varying degrees of short stature and disproportion of limbs. People with mild symptoms may never be diagnosed. The body of a person with hypochondroplasia appears short and broad with a long torso and short limbs. Life span is normal. Like achondroplasia, hypochondroplasia is inherited in an autosomal dominant manner.
ECTODERMAL DYSPLASIAS Ectodermal dysplasias affect the growth and development of tissues derived from the early outer layer of embryonic tissue known as the ectoderm. Tissues derived from the ectoderm include hair, fingernails, skin, sweat glands, and teeth. People with ectodermal dysplasias display abnormalities in at least two derivatives of the ectoderm. Ectodermal dysplasia (ED) can take many different forms because so many tissues are derived from the ectoderm. Over 150 types of ectodermal dysplasias have been identified.
The effects of ectodermal dysplasias range from mild to severe. They are divided into two major groups based on the presence or absence or normal sweating. Sweat production is normal in hidrotic (sweating) types and reduced in hypohidrotic (decreased sweating) types. Types with reduced or absent sweating are generally more severe.
Christ-Siemens-Touraine syndrome (CST), a hypohidrotic (decreased sweating) ectodermal dysplasia, is a common, well-understood type of ectodermal dysplasia. People with this type of ectodermal dysplasia are not able to sweat or form tears normally. They are very sensitive to light and are not able to control their body temperature well due to their reduced sweating. Intelligence is normal. People with CST often have small or missing teeth, eyebrows, and eyelashes. Head hair is usually sparse, but fingernails are normal. CST is usually X-linked recessive, affecting only males with full symptoms of the disease. In some cases, female carriers show mild symptoms of the disease. Rarer autosomal dominant and autosomal recessive forms can affect males and females.
Clouston ectodermal dysplasia, a hidriotic (sweating) ectodermal dysplasia, also known as ectodermal Dysplasia 2 (ED2) is found more commonly in people of French Canadian descent. People with this form of ED have partial to total baldness with normal teeth, severely abnormal fingernails, and darkly pigmented areas of skin, especially over joints. They have underdeveloped eyebrows and eyelashes and may be born with teeth. They may also have thickened skin on the soles of their feet and the palms of their hands. Features including mental retardation and strabismus, or crossed eyes, may occur with this disorder, however intelligence is usually normal. This form of ED is inherited in an autosomal dominant manner. Any affected person has a 50% chance to pass the disorder to each of their children.
BOOKS
Moore, Keith L. The Developing Human: Clinically Oriented Embryology. Philadelphia: W.B. Saunders Company, 1998.
PERIODICALS
Wright, Michael J. "Hypochondroplasia." Gene Map Locus (2001): 16.
ORGANIZATIONS
American Cancer Society. 1599 Clifton Rd. NE, Atlanta, GA 30329. (800) 227-2345. <http://www.cancer.org>.
Children's Craniofacial Association. PO Box 280297, Dallas, TX 75243-4522. (972) 994-9902 or (800) 535-3643. contactcca@ccakids.com. <http://www.ccakids.com>.
FACES: The National Craniofacial Assocation. PO Box 11082, Chattanooga, TN 37401. (423) 266-1632 or (800) 332-2373. faces@faces-cranio.org. <http://www.facescranio.org/>.
Greenberg Center for Skeletal Dysplasias. 600 North Wolfe St., Blalock 1012C, Baltimore, MD 21287-4922. (410) 614-0977 <http://www.med.jhu.edu/Greenberg.Center/Greenbrg.htm>.
Johns Hopkins University-McKusick Nathans Institute of Genetic Medicine 600 North Wolfe St., Blalock 1008, Baltimore, MD 21287-4922. (410) 955-3071.
Little People of America, Inc. National Headquarters, PO Box 745, Lubbock, TX 79408. (806) 737-8186 or (888) LPA-2001. lpadatabase@juno.com. <http://www.lpaonline.org>.
National Foundation for Ectodermal Dysplasias. PO Box 114, 410 E Main, Mascoutah, IL 62258-0114. (618) 566-2020. Fax: (618) 566-4718. <http://www.nfed.org>.
National Organization for Rare Disorders (NORD). PO Box 8923, New Fairfield, CT 06812-8923. (203) 746-6518 or (800) 999-6673. Fax: (203) 746-6481. <http://www.rarediseases.org>.
