The association between consanguineous marriage and offspring with congenital hearing loss

BACKGROUND

Consanguinity is a commonly recognized practice among marriages in the Middle East and may lead to an increase in the prevalence of inherited disorders. Autosomal recessive deafness is the most common form of inherited congenital hearing loss (CHL).

OBJECTIVES

Determine the association of consanguineous marriages with congenital sensorineural hearing loss (SNHL) and auditory neuropathy.

DESIGN

Descriptive and analytical cross-sectional study.

SETTING

Ear specialist hospital.

PATIENTS AND METHODS

Children with severe-to-profound congenital SNHL, who had been referred to the specialist hospital for cochlear implant were analyzed. Patients were divided into subgroups based on degree of consanguinity.

MAIN OUTCOME MEASURE

The relative risk of having more than one child with SNHL in offspring of a consanguineous marriage.

SAMPLE SIZE

189 parents and children with CHL.

RESULTS

The parents of 157 children (83.1%) were blood-related. Of those, 48 had more than one child with CHL (31.4%), while only two parents who were not blood-related had more than one child with CHL (6.25%; P=.005). Among the 189 children, 131 (69.3%) parents were direct cousins. Only 39 (20.6%) and 43 (22.8%) children had family histories of CHL on the paternal and maternal sides, respectively. There was no statistically significant difference in the prevalence of auditory neuropathy between the offspring of consanguineous and non-consanguineous marriages (P=.648).

CONCLUSION

The risk of having more than one child with SNHL in the offspring from a consanguineous marriage is 3.5 times higher than that of a non-consanguineous mating.

LIMITATION

The association of hearing loss degree with consanguinity was not studied.

CONFLICT OF INTEREST

None.

PMP22 Gene-Associated Neuropathies: Phenotypic Spectrum in a Cohort from India

Reports of spectrum of clinical manifestations in PMP22 gene-associated neuropathies (duplication/mutations) are scarce. To identify the frequency of PMP22 gene variations and establish their genotype-phenotype correlation. Patients with suspected genetic demyelinating neuropathy (n = 128) underwent evaluation for copy number variations and point mutations in PMP22 gene by multiplex ligation-dependent probe amplification (MLPA) and direct sequencing respectively. Of these, only 27 patients (M:F:19:8) from 18 families had PMP22 gene-associated neuropathy; they were subsequently analyzed for genotype-phenotype correlation. Twenty-five patients had PMP22 duplication while two patients had PMP22 missense mutations (p.A114V and p.L80P). Age at onset of neuropathy ranged from infancy to 63 years and symptom duration ranged from 2 to 32 years. Cranial nerve dysfunction in the form of ptosis, ophthalmoplegia, bifacial weakness, and sensorineural hearing loss was observed in addition to a number of systemic features. Three patients were asymptomatic. All except one patient were ambulant. Velocity of median nerve and amplitude of evoked motor responses from common peroneal nerve were significantly reduced in male patients. There was significantly worse disability in the late-onset group as compared with the early-onset group. Otherwise, the mean age at onset, frequency of skeletal deformities, patterns of motor weakness, muscle stretch reflexes, sensory impairment, disability rating scales, and electrophysiological parameters were comparable irrespective of gender, onset age, family history and ulnar nerve conduction velocities. The relatively low frequency of PMP22 duplication in the present cohort warrants a more comprehensive search to establish the genetic etiology. Further research into the role of other genetic variants as well as modifier genes and their effect on phenotypic heterogeneity is indicated.