Introduction:
Hearing loss has been seen in all the cases of stickler syndrome. This is because of the data gained from the audiometry test, which states that almost sixty-seven percent of the cases. Although hearing loss was not initially associated with Stickler’s syndrome, over the period, this condition was seen to be associated with different types of genes due to cell mutations. Hearing loss is seen as a rare entity depending on the type of gene changes and the patient's age. Such hearing loss associated with Stickler’s syndrome requires medical help.
What Is Stickler’s Syndrome?
Sticker’s syndrome is a type of genetic disorder (autosomal dominant) named after an American German pediatrician. This condition is characterized by short-sightedness, blindness of the retina, loosening of the joints, improperly developed surfaces of the articulation surfaces and prematurely occurring wear and tear of the bones, cleft in the palate, inflammation of the bones, underdeveloped midface and jaw bone. This condition was also seen with sensory nerve-induced hearing loss and minimal changes in the epiphyses. The most common features that differentiate Stickler’s syndrome include four systemic symptoms: the eyes, face and mouth, the bones, and the ears associated with changes in collagen.
What Are the Types of Sticklers Syndrome?
Sticker syndrome is a disorder of the connective tissues, seen involving changes in the eyes, bones, ears, and face. Based on the changes in the genes, six different types of Stickler’s syndrome are associated with different types of symptoms.
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Type 1: Here, the type of collagen genes involved is COL2A1 and is seen as autosomal dominant, showing mild hearing loss.
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Type 2: Here, the type of collagen genes involved is COL11A1 and is seen as both autosomal dominant and recessive disorder showing severe to moderate hearing loss.
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Type 3: Here, the collagen genes involved are COL11A2, which is seen as an autosomal dominant disorder showing moderate hearing loss.
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Type 4: Here, the type of collagen genes involved is COL9A1, an autosomal recessive disorder showing moderate to severe hearing loss.
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Type 5: Here, the collagen genes involved are COL9A2, which is seen as an autosomal recessive disorder showing moderate to severe hearing loss.
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Type 6: Here, the type of collagen genes involved are COL9A3, LRP2, LOXL3, and BMP4, which is seen as autosomal dominant as well as a recessive disorder showing moderate to severe hearing loss, while in some cases, normal hearing is seen.
How Does Hearing Loss Vary in Each Type of Sticklers Syndrome?
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Hearing Loss Seen in Type 1 Stickler Syndrome: The cause of Stickler syndrome is a multi-cellular division (mutation) occurring in the COL2A1 gene. Around 52 percent of people with Stickler's syndrome show an inability to hear. This is often recorded by taking a history or hearing test (audiometry). Also, there is no exact correlation between hearing loss and aging in patients with Stickler syndrome. By conducting tests like the DPOAE (distortion product otoacoustic emission test) to test the level of amplification the ear could take, it was seen that there was a gradual decrease in hair cells on the outer ear, indicating the hearing loss as a sensorineural type (sensory nerve). In type 1 stickler syndrome, although the hearing loss is due to a defect in sensory origin, it appears mostly symmetrical. It is seen in all age groups, including children, mainly limited to the middle ear. The most common incidence is seen in the caucasian population due to their higher incidence of otosclerosis (thinning of the bone) associated with Stickler's syndrome. Also, one can say that this similar type of hearing loss defect in the gene is seen in a condition called presbycusis (a clinical condition characterized by hearing loss in both ears due to aging)
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Hearing Loss Seen in Type 2 to 3 Stickler Syndrome: Hearing loss is mostly similar in both type 2 and 4 Stickler syndromes. However, these conditions are comparatively more intense than STL1. The average global prevalence is around seventy to eighty-three percent. In this type, the patients show a type of hearing loss that is low to medium with mild to moderate frequencies, and medium to severe hearing loss is seen in patients when high frequencies are played. Hearing loss is also progressing with age and is higher when compared to type 1 Stickler syndrome. However, the age at which the condition typically occurs is not noted but is seen minimally in childhood. No defect in the skull's temporal bone is noted in any radiological study while a computed tomography is performed. The defective genes include COL11A1 and COL11A2, consisting of type eleven collagen components present predominantly in the body.
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Hearing Loss Seen in Type 4 to 6 Stickler Syndrome: In this type, hearing loss is often seen due to single or multiple types of cellular mutations. This includes the type 9 collagen cells. In this type, patients with sensory-related hearing loss also show short-sightedness, dysplasia of the long bones, retinopathy, defects in the palate, etc. This condition is seen to occur as a congenital condition (from the womb), although the exact status is unknown. The hearing loss is seen to be more in higher frequencies.
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Hearing Loss in Stickler Syndrome With Its Mutation in Non-Collagen-Associated Genes: This type of hearing loss is seen in Stickler’s syndrome, which does not show any division in the collagen. The genes affected in this condition are LRP2. Here, patients also show a weakening of the joints, short-sightedness, and cataracts (calcification of the lenses). Here, the progression of the hearing loss is identified by using methods like an audiogram, which, over the period, gives a graphic representation of hearing loss.
Conclusion:
These are the different types of hearing loss associated with Stickler’s syndrome. Although hearing loss is one common entity, the cause and means of origin, like sensory or motor, varies from one type to another. As the name indicates, Stickler syndrome is a group of phenomena that include several health problems. Hence, it is important to understand each type to differentiate the cause and the treatment needed. Also, it is necessary to take radiographic and genetic testing in children to rule out the onset of Stickler’s syndrome as a means of prevention.
