LETTER TO JMG

Distinctive audiometric features between USH2A and USH2B subtypes of Usher syndrome

M Hmani-Aifa¹, S Ben Arab², K Kharrat³, D J Orten⁴, A Boulila-Elgaied¹, M Drira³, S Hachicha^2,5, W J Kimberling⁴, H Ayadi¹

¹ Laboratoire de Génétique Moléculaire Humaine, Faculté de Médecine, 3018 Sfax, Tunisia
² Unité de Génétique Epidémiologique, Faculté de Médecine, 1007 Tunis, Tunisia
³ Service d'ORL, CHU Bourguiba, Sfax, Tunisia
⁴ The Center for the Study and Treatment of Usher syndrome, Boys Town National Research Hospital, Omaha, NE 68131, USA
⁵ Service d'ORL et de Chirurgie Maxillo-faciale, Hôpital La Rabta, 1007 Tunis, Tunisia

Correspondence to:
Correspondence to:
Dr H Ayadi, Laboratoire de Génétique Moléculaire Humaine, Faculté de Médecine, 3018 Sfax, Tunisia;
Hammadi.Ayadi@fmsf.rnu.tn

Keywords: Usher syndrome; USH2A and USH2B subtypes; retinitis pigmentosa; audiometry

Abbreviations: USH, Usher syndrome; RP retinitis pigmentosa; ACPTA, air conduction pure tone average

Usher syndrome (USH) is an autosomal recessive disorder characterised by hearing impairment and retinitis pigmentosa (RP). The prevalence of USH varies from one population to another, for example, 3-4.4 per 100 000 in Scandinavian and North American populations^{1, 2} and 6.2-10 per 100 000 in the city of Birmingham, UK.³ This syndrome is clinically heterogeneous and three clinical forms have been described⁴: (1) USH type I (USH1) is characterised by severe to profound congenital deafness, constant vestibular dysfunction, and prepubertal onset of RP; (2) USH type II (USH2) is characterised by congenital moderate to severe deafness, absence of vestibular dysfunction, and onset of RP usually in the late second to early third decade; (3) USH type III (USH3) is characterised by postlingual progressive deafness, occasional vestibular dysfunction, and progressive RP with a variable age of onset (see also http://www.ncbi.nlm.nih.gov/omim). Usher syndrome is also genetically heterogeneous; at least six distinct . . . [Full text of this article]

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