Lesser Known Disorders
Each issue of this series contains at least three lesser known disorders. Some of these disorders may contain subtypes which will also be presented. You will also notice that each disorder has a code. These codes represent the coding system for all disabilities and disorders listed in the Educator’s Diagnostic Manual(EDM) Wiley Publications.
VI 3.03-Aniridia
Disability Category – Visual Impairment
Definition
Aniridia is a congenital malformation of the eye in which the iris is not completely formed and that results in cataract formation and congenital glaucoma (Office of Rare Diseases, 2005).
Explanation
If there is no iris in the eye it is impossible to control the inlet of light—the iris is an analogue to the aperture of the camera. The pupil stands wide open, no matter how light it is. The only treatment of aniridia is as yet the use of colored eye lenses in order to reduce the light inlet.
Aniridia literally means “without iris.” In most cases this is the most visible sign of the condition. However, aniridia is Caused when the gene responsible for eye development—the PAX6 gene—does not function correctly. This causes the eye to stop developing too early and when the baby is born most of the eye is underdeveloped to some degree.
According to Trout (2004, p.1), in terms of inheritance, there are 4 basic “types” of Aniridia. These are:
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VI 3.03a-Familial Aniridia (Autosomal Dominant)
This is the most common form of Aniridia. It is inherited directly from a parent who has Aniridia themselves. It is the result of a mutation in a gene called the “PAX6” gene. Familial Aniridia is associated with many serious ocular (eye) conditions, including cataracts, glaucoma, and corneal pannus. Close follow-up by an experienced ophthalmologist is very important. Each child of a person with familial Aniridia will have a 50% chance of inheriting the gene mutation.
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VI 3.03b-Gillespie Syndrome (Autosomal Recessive)
This type of Aniridia is extremely rare. It may be inherited through parents who do not have Aniridia themselves, but who both have one normal copy of the PAX6 gene, and one mutated copy. This type of Aniridia is associated with a particular appearance of the iris remnant (described as having a “scalloped” border) mental retardation, and cerebellar ataxia, (muscle incoordination). There are reports of more than one case of Gillespie syndrome in a family. There have also been reports of people with Gillespie syndrome whose children also have the disorder.
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VI 3.03c-Sporadic Aniridia (no deletion detected)
This type of Aniridia is the second most common form. Both parents have normal chromosomes. The affected person has a “new” mutation of the PAX6 gene (a mutation which occurred before or very soon after conception) It is not known what causes this mutation. People with sporadic Aniridia are at risk for the same eye complications as those with Familial Aniridia.
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VI 3.03d-WAGR Syndrome
This type of Aniridia is rare. Both parents have normal chromosomes. The affected person has a “new” mutation (as in Sporadic Anridia, above). Unlike Sporadic Aniridia, however, this new mutation involves not only the PAX6 gene, but a large number of neighboring genes as well. This genetic abnormality is a “deletion,” or set of missing genes, which are located on the short arm of chromosome number 12. In addition to Aniridia, children with WAGR syndrome have a high risk for Wilms tumor (a type of cancer of the kidney) and other medical complications, such as genital abnormalities, and learning and behavior difficulties.
OHI 14.01 – Acromegaly
Disability Category-Other Health Impaired
Definition
Acromegaly is the Greek word for “extremities” and “enlargement.” When the pituitary gland produces excess growth hormones, this results in excessive growth — called acromegaly. The excessive growth occurs first in the hands and feet, as soft tissue begins to swell. Acromegaly affects mostly middle-aged adults. Untreated, the disease can lead to severe illness and death (University of Maryland Medical Center, 2004). Acromegaly is a serious systemic condition caused in over 98% of cases by an adenoma (i.e., benign tumor) of the pituitary gland that secretes excessive growth hormone (GH) (Pituitary Network Association, 2005).
Explanation
Symptoms of acromegaly vary depending on how long the patient has had the disease. The following are the most common symptoms. However, each individual may experience symptoms differently (Pituitary Network Association, 2005; University of Maryland Medical Center, 2004):
- Arthritis
- Carpal tunnel syndrome
- Colon polyps and colon cancer
- Diabetes mellitus
- Enlargement of forehead (frontal bossing) and jaw (prognathism) with pronounced under- or overbite, spreading teeth, and enlarging tongue
- Enlargement of hands (ring size), feet (shoe size) and head (hat size)
- Headaches
- Heart disease and heart enlargement (cardiomegaly and left ventricular hypertrophy)
- Hypertension
- Impotence, loss of libido
- Interrupted menstrual cycle (amenorrhea)
- Lactation (galactorrhea)
- Loss of vision
- Oily skin and excessive sweating
- Sleep apnea
- Soft tissue thickening of the palms of the hands and soles of the feet
- Tiredness, fatigue, depression
HI 2.01-Cholesteatoma
Disability Category – Hearing Impairment
Definition
Cholesteatoma can be a congenital (present at birth) defect, but it more commonly occurs as a complication of chronic ear infection. Long-term inflammation and malfunction of the eustachian tube leads to chronic negative pressure in the middle ear (U.S. National Library of Medicine, 2004).
Explanation
According to the American Academy of Otolaryngology (2004), a Cholesteatoma is a skin growth that occurs in an abnormal location, the middle ear behind the eardrum. It is usually due to repeated infection, which causes an ingrowth of the skin of the eardrum.
Cholesteatomas often take the form of a cyst or pouch that sheds layers of old skin that builds up inside the ear. Over time, the cholesteatoma can increase in size and destroy the surrounding delicate bones of the middle ear. Hearing loss, dizziness, and facial muscle paralysis are rare but can result from continued cholesteatoma growth.
HI 2.01a-Acquired Cholesteatoma
A type of Cholesteatoma that occurs after birth
HI 2.01b-Congenital Cholesteatoma
A type of Cholesteatoma that is present from birth
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