Usher syndrome is the most common genetic form of deaf-blindness. This disorder is characterized by congenital sensorineural hearing loss associated with defects in the inner ear, and vision loss associated with retinitis pigmentosa. In most cases, the rod cells are affected first, followed by the cone cells. In some cases, the foveal vision is spared, resulting in a 'doughnut vision'. According to the severity of the condition, three distinct types of Usher syndromes are recognized. Usher syndrome type 1 is the most severe of these different types. Patients affected with this type are born profoundly deaf, and start to lose their vision within the first decade of their life. In addition, problems in the vestibular system are also seen, resulting in patients exhibiting difficulties in maintaining their balance and a significant delay in walking as infants. Approximately, 5% of children born deaf are actually affected by Usher syndrome type 1. Overall, the incidence of this severe type is about 4 per 100,000, although it is more common in certain populations, such as Ashkenazi Jews and the Acadian population in Louisiana.
Since the vision loss does not occur until much later, a diagnosis of Usher syndrome can be missed out in the face of deafness as the only symptom in infancy. Molecular diagnostic testing has the potential to provide an early diagnosis. The condition, however, cannot be cured. Management strategies include cochlear implant, and preparing for blindness before it manifests itself.
In a study comprising 50 children with congenital sensorineural hearing loss (SNHL) attending the Ear, Nose, and Throat Department of Al-Ramadi Teaching Hospital in Al-Ramadi city (December 2007 to October 2008), Al-Ani et al. (2009) diagnosed two children with profound bilateral SNHL. Upon ophtalmological examination, the children were found to have hearing loss and retinitis pigmentosa and were diagnosed as having Usher syndrome.
Ben-Salem et al. (2014) described a nuclear consanguineous family of Iraqi origin with one child affected with profound sensorineural hearing loss. The parents and the patient’s one other sibling were phenotypically normal. The affected child had normal developmental milestones and was of normal intelligence. Fundoscopic examination and ERG also revealed normal results. Molecular analysis identified a novel homozygous variant in the MYO7A gene in the patient.
Shuja-ud-din et al. (2002) reported the case of a 50-year old Kuwaiti woman as the first case to be diagnosed with Usher syndrome Kuwait. Usher syndrome in this patient was also found to have an unusual comorbid association with hypothyroidism due to autoimmune thyroid disease.
[Shuja-ud-din, Al Adsani A, Baidas G. Autoimmune thyroid disease in a patient with Usher's syndrome: case report. Kuwait Med J. 2002; 34(2):150-2.]
[See: Iraq > Ben-Salem et al., 2014].