Hearing impairment in persons with the hemoglobin SC genotype

June 30, 2010
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Abstract

The hemoglobin (Hb) SC genotype is seen in persons who have inherited the gene for hemoglobin S from one parent and the gene for hemoglobin C from the other. Some people with this genotype develop Hb SC disease, a variant of sickle cell disease. Hb SC disease, a compound heterozygous condition, is the most common of the hemoglobinopathies and the least severe, although it is still serious. One of the documented complications of the presence of the Hb SC genotype is sensorineural hearing loss (SNHL). We conducted a prospective case-control study of 43 subjects, aged 15 to 65 years, who had the Hb SC genotype to determine the incidence of SNHL and to determine if the hearing loss in these subjects was correlated with sex or age. Our control group was made up of 100 generally healthy, sex- and age-matched subjects with the normal Hb AA genotype. SNHL was defined as a loss of more than 25 dB HL at two or more frequencies in the same ear or at one or more frequencies in both ears. We found that SNHL was present in 12 of the 43 subjects (27.9%) in the Hb SC group (17 of 86 ears [19.8%]) and in 17 of the 100 subjects (17.0%) in the Hb AA group (21 of 200 ears [10.5%]; the difference between the two groups was not statistically significant (χ2 = 1.589; p = 0.105). We found that in the Hb SC group, SNHL was more common among females than males (38.5 vs. 11.8%), although the difference was not quite significant statistically (χ2 = 2.435; p = 0.056); in the Hb AA group, the incidence was fairly equal-15.4 and 18.8%, respectively (χ2 = 0.033; p = 0.427). Therefore, we conclude that the hearing loss in the subjects of this study was not correlated with the presence of the Hb SC genotype in either sex. In terms of age, SNHL was significantly more common in subjects aged 41 to 65 years than in those aged 15 to 40 years in both genotype groups. In the Hb SC group, SNHL was present in 4 of the 33 younger subjects (12.1%) and in 8 of the 10 older subjects (80.0%) (χ2 = 14.354; p < 0.001). In the Hb AA group, the corresponding figures were 7 of 85 (8.2%) and 10 of 15 (66.7%) (χ2 = 26.840; p < 0.001). Therefore, we conclude that the hearing loss in the subjects of this study was a function of age and was not associated with the presence of the Hb SC genotype.

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