Mental retardation or intellectual disabilities are neurodevelopmental disorders which primarily affect an individual’s functional abilities, particularly cognition and occupational functioning.
eurodevelopmental disorders primarily originate from genetic factors; however, their onset is partially linked to other physiological factors such as diet and medical history. Because of various possible genetic abnormalities, the development of many different and abnormal neurodevelopmental conditions is also possible.
A particular presentation of a genetic abnormality is an X-linked mental retardation (XLID) that accounts for 5% to 10% of all cases of intellectual disability. While Fragile X syndrome is a common manifestation of this abnormality, current researchers are interested in studying more uncommon conditions such as the X-linked mental retardation, abidi type. The abidi syndrome is a rare genetic disorder characterized by observable physical abnormalities including short stature, small head circumference, sloping forehead, and underdevelopment of the testes. The condition is more common among males than females, and is relevant among males between 16 to 50 years of age.
Abidi X-linked mental retardation could be inherited through generations. A 1999 study on the emergence of abidi syndrome in one particular family found that the disorder affected eight males in just three generations. Majority of family members diagnosed with abidi syndrome presented with a similar symptomatology including small head circumference, short stature, sloping forehead, and small testes.
Causes of Abidi X-Linked Mental Retardation Syndrome
Abidi X-linked mental retardation is primarily caused by mutations in the Xq24-q25 genetic region; however, the exact cause of such genetic mutation or abnormality is not known. Researchers have also tried to provide other possible causes which may be linked to the development and progression of abidi X-linked mental retardation. The following table showcases other possible causes related to the condition.
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Conductive hearing loss
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Exostosis
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Ossicular chain defect, disruption, or fixation
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Disorders in the external auditory canal
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Impacted cerumen
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Sensorineural hearing loss
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Atresia of the external auditory canal
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Otitis media with effusion
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Inner ear malformations
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Otitis externa
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Perforation of the tympanic membrane
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Labyrinthineaplasia
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Middle ear disorders
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Acute and chronic otitis
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Common cavity malformation
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Hemotympanum
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Tympanosclerosis
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Prematurity
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Cochlear malformations
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Large vestibular aqueduct
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Drugs
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Hypoxic-ischemic encephalopathy
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Trauma and infection
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Ménière disease
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Perilymph fistula
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Neoplasm
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Diagnostic Clinical Features
The physical features of abidi X-linked mental retardation do not appear upon birth, rather they progress during the prepubertal period. During this time, it could be evidently noticed that the stature, head circumference, and forehead would cease to develop. The same occurs in testicular development. However, prior to these manifestations of abidi syndrome, significant cognitive problems appear in terms of memory, problem solving, attention, or comprehension.
The following are primary clinical features associated with abidi X-linked mental retardation.
- Short stature
- Small head circumference
- Sloping forehead
- Hearing loss
- Cupped ears
- Testicular abnormalities
- Cognitive impairment, with IQ falling between 12 to 62
Generally, growth and development factors are associated with abidi X-linked mental retardation. Researches, however, found that the disorder does not affect muscle development.
Treating Abidi X-Linked Mental Retardation Syndrome
With the condition being a rare genetic disorder, there is currently no direct treatment for abidi X-linked mental retardation. However, because of modern medical advances, the prevention of such disorder is possible. Efforts to alleviate XLID have found that gamete donation may be a possible method for preventing the progression of the disorder. Along with this, sufficient prenatal diagnosis and genetic counselling should be done.
Further Reading