National Journal of Medical Research (Mar 2012)
KARYOTYPE STUDY IN PATIENTS WITH HEARING DISABILITY
Abstract
Background: Hearing disability is the most common sensory disorder in humans. About 50% cases of congenital hearing loss are due to genetic causes. About 70% of genetic hearing loss is nonsyndromic and 30% is syndromic. Syndromic hearing loss is found as about 500 syndromes associated with chromosomal abnormalities. Genetic study of hearing loss include numerical chromosomal aberrations like trisomy 13, 18, 21 and structural chromosomal aberrations like deletion, translocation or invertion involving chromosome numbers 1, 2, 3, 5, 6, 7, 8,10,11, 12, 13, 15, 18, 21 and many more . Materials & Method: The aim of this study was to carry out a cytogenetic profile of 25 clinically diagnosed patients of hearing loss from school of deaf & dumb and from ENT clinics, Ahmedabad to find out the chromosomal abnormalities in these patients. Karyotypes of all the patients were prepared from peripheral venous blood & photographed at genetic laboratory at B.J.Medical College, Ahmedabad. Observations: Clinical & karyotype analysis revealed that out of 25 patients, 8 cases had positive family history of hearing loss. Positive history of consanguineous marriage was found in 6 patients. It was observed that 17(68%) cases had isolated(non-syndromic) hearing loss and 8(32%) cases had syndromic deafness. Among 17(68%) non-syndromic patients 13(52%) cases showed normal chromosomal constitution and in 4(16%) cases metaphase was not found and out of 8(32%) patients with syndromic deafness, one female (4%) & two males (8%) had trisomy 21, one female (4%) had monosomy of X chromosome and 4(16%) cases showed normal chromosomal constitution. Conclusion: Cytogenetic pattern of hearing loss is variable among different studies.So, cytogenetic analysis of suspected hearing loss is of value to objectively confirm the diagnosis and to provide a basis for genetic counselling.
