Scheie syndrome is a disease caused by a deficiency in the
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
iduronidase, leading to the buildup of
glycosaminoglycans
Glycosaminoglycans (GAGs) or mucopolysaccharides are long, linear polysaccharides consisting of repeating disaccharide units (i.e. two-sugar units). The repeating two-sugar unit consists of a uronic sugar and an amino sugar, except in the case ...
(GAGs) in the body. It is the most mild subtype of
mucopolysaccharidosis type I
Mucopolysaccharidosis type I is a spectrum of diseases in the mucopolysaccharidosis family. It results in the buildup of glycosaminoglycans (or GAGs, or mucopolysaccharides) due to a deficiency of alpha-L iduronidase, an enzyme responsible for t ...
; the most severe subtype of this disease is called
Hurler Syndrome
Hurler syndrome, also known as mucopolysaccharidosis Type IH (MPS-IH), Hurler's disease, and formerly gargoylism, is a genetic disorder that results in the buildup of large sugar molecules called glycosaminoglycans (GAGs) in lysosomes. The inab ...
.
Scheie syndrome is characterized by corneal clouding, facial dysmorphism, and normal lifespan. People with this condition may have
aortic regurgitation
Aortic regurgitation (AR), also known as aortic insufficiency (AI), is the leaking of the aortic valve of the heart that causes blood to flow in the reverse direction during ventricular diastole, from the aorta into the left ventricle. As a conseq ...
.
Symptoms
The symptoms of Scheie syndrome are variable, but are milder than Hurler Syndrome. Symptoms may begin to appear by age 5, but affected children are often not diagnosed until after age 10. Patients with Scheie Syndrome may have normal intelligence, or they may have mild learning impairments or psychiatric problems.
Glaucoma
Glaucoma is a group of eye diseases that result in damage to the optic nerve (or retina) and cause vision loss. The most common type is open-angle (wide angle, chronic simple) glaucoma, in which the drainage angle for fluid within the eye rem ...
,
retinal degeneration, and clouded
cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power ...
s may cause visual impairments.
Aortic valve
The aortic valve is a valve in the heart of humans and most other animals, located between the left ventricle and the aorta. It is one of the four valves of the heart and one of the two semilunar valves, the other being the pulmonary valve. The ...
disease may be present, along with
carpal tunnel syndrome
Carpal tunnel syndrome (CTS) is the collection of symptoms and signs associated with median neuropathy at the carpal tunnel. Most CTS is related to idiopathic compression of the median nerve as it travels through the wrist at the carpal tunn ...
, deformed hands and feet, stiff joints, or
sleep apnea
Sleep apnea, also spelled sleep apnoea, is a sleep disorder in which pauses in breathing or periods of shallow breathing during sleep occur more often than normal. Each pause can last for a few seconds to a few minutes and they happen many times ...
. People with Scheie syndrome may live into adulthood.
[
]
Genetics
Children with Scheie Syndrome carry two defective copies of the ''IDUA'' gene, which has been mapped to the 4p16.3 site on chromosome 4
Chromosome 4 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 4 spans more than 186 million base pairs (the building material of DNA) and represents between 6 and 6.5 percent of the t ...
. This is the gene which encodes for the protein iduronidase. All patients with subtypes of MPS I have mutations in the same gene, leading to deficiencies of the same enzyme. However, patients with Scheie Syndrome have a greater level of iduronidase activity than patients with Hurler Syndrome.
Because Scheie syndrome 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 allosome, allosomal (sex chromosome) pairs, which may have different structures. The DNA in au ...
recessive
In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and t ...
disorder, affected persons have two nonworking copies of the gene. A person born with one normal copy and one defective copy is called a carrier
Carrier may refer to:
Entertainment
* ''Carrier'' (album), a 2013 album by The Dodos
* ''Carrier'' (board game), a South Pacific World War II board game
* ''Carrier'' (TV series), a ten-part documentary miniseries that aired on PBS in April 20 ...
. They will produce less α-L-iduronidase than an individual with two normal copies of the gene. The reduced production of the enzyme in carriers, however, remains sufficient for normal function; the person should not show any symptoms of the disease.
History
In 1919, Gertrud Hurler, a German pediatrician, described a syndrome involving corneal clouding, skeletal abnormalities, and intellectual disability. This became known as Hurler Syndrome.
See also
* Hunter syndrome
Hunter syndrome, or mucopolysaccharidosis type II (MPS II), is a rare genetic disorder in which large sugar molecules called glycosaminoglycans (or GAGs or mucopolysaccharides) build up in body tissues. It is a form of lysosomal storage disease. ...
(MPS II)
* Sanfilippo syndrome
Sanfilippo syndrome, also known as mucopolysaccharidosis type III (MPS III), is a rare autosomal recessive lysosomal storage disease that primarily affects the brain and spinal cord. It is caused by a buildup of large sugar molecules called glyc ...
(MPS III)
* Morquio syndrome
Morquio syndrome, also known as Mucopolysaccharidosis Type IV (MPS IV), is a rare metabolic disorder in which the body cannot process certain types of sugar molecules called glycosaminoglycans (AKA GAGs, or mucopolysaccharides). In Morquio syndr ...
(MPS IV)
References
External links
{{Mucopolysaccharidoses
Proteoglycan metabolism disorders
Syndromes