Tietz syndrome
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Tietz syndrome, also called Tietz albinism-deafness syndrome or albinism and deafness of Tietz, is an
autosomal An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosomal (sex chromosome) pairs, which may have different structures. The DNA in autosom ...
dominant
congenital disorder A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities c ...
characterized by
deafness Deafness has varying definitions in cultural and medical contexts. In medical contexts, the meaning of deafness is hearing loss that precludes a person from understanding spoken language, an audiological condition. In this context it is written ...
and
leucism Leucism () is a wide variety of conditions that result in the partial loss of pigmentation in an animal—causing white, pale, or patchy coloration of the skin, hair, feathers, scales, or cuticles, but not the eyes. It is occasionally spelled ...
. It is caused by a mutation in the
microphthalmia-associated transcription factor Microphthalmia-associated transcription factor also known as class E basic helix-loop-helix protein 32 or bHLHe32 is a protein that in humans is encoded by the ''MITF'' gene. MITF is a basic helix-loop-helix leucine zipper transcription facto ...
(MITF) gene. Tietz syndrome was first described in 1963 by Walter Tietz (1927–2003) a German Physician working in California.


Presentation

Tietz syndrome is characterized by profound hearing loss from birth, white hair and pale skin (hair color may darken over time to blond or red). The hearing loss is caused by abnormalities of the inner ear (
sensorineural hearing loss Sensorineural hearing loss (SNHL) is a type of hearing loss in which the root cause lies in the inner ear or sensory organ (cochlea and associated structures) or the vestibulocochlear nerve (cranial nerve VIII). SNHL accounts for about 90% of re ...
) and is present from birth. Individuals with Tietz syndrome often have skin and hair color that is lighter than those of other family members. Tietz syndrome also affects the eyes. The iris in affected individuals is blue, and specialized cells in the eye called
retinal pigment epithelial The pigmented layer of retina or retinal pigment epithelium (RPE) is the pigmented cell layer just outside the neurosensory retina that nourishes retinal visual cells, and is firmly attached to the underlying choroid and overlying retinal visual ...
cells lack their normal pigment. The changes to these cells are generally detectable only by an eye examination; it is unclear whether the changes affect vision.


Cause

Tietz syndrome is caused by mutations in the
MITF Microphthalmia-associated transcription factor also known as class E basic helix-loop-helix protein 32 or bHLHe32 is a protein that in humans is encoded by the ''MITF'' gene. MITF is a basic helix-loop-helix leucine zipper transcription fact ...
gene, located on human
chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins ar ...
3p14.1-p12.3. It is inherited in an autosomal dominant manner. This indicates that the defective gene responsible for a disorder is located on an
autosome An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosomal (sex chromosome) pairs, which may have different structures. The DNA in autosomes ...
(chromosome 3 is an autosome), and only one copy of the defective gene is sufficient to cause the disorder, when inherited from a parent who has the disorder.


Treatment


See also

*
List of cutaneous conditions Many skin conditions affect the human integumentary system—the organ system covering the entire surface of the body and composed of skin, hair, nails, and related muscle and glands. The major function of this system is as a barrier agai ...


References


External links

* {{DEFAULTSORT:Tietz Albinism-Deafness Syndrome Autosomal dominant disorders Rare genetic syndromes Disturbances of human pigmentation Transcription factor deficiencies Rare syndromes Syndromes with sensorineural hearing loss