World's Largest Family With Inherited Hearing Loss

July 20, 2007 Updated: July 20, 2007

Hidden deep in China's Jiangsu Province, far off the beaten track, there is a small village with a very large family. The family, while known for its size, has instead become the subject of research because of a hearing loss passed down over its generations.

After more than 20 years of clinical and molecular genetic research, medical experts from Jiangsu Province have only recently straightened out the family's clinical characteristics, genetic phenotype, and the mutant factors causing the loss of hearing.

Nanjing-based Jinling Evening Paper reported that, according to Professor Bo Xingkuan from the Otorhinolaryngology (ear, nose and throat or ENT) Department of Jiangsu People's Hospital, research on the family began in 1983 after a letter was received telling of a large family in a small, secluded village in Huaian City of Jiangsu, of which many members have suffered hearing loss for reasons unknown. Led by Professor Bo Xingkuan, a project team was formed and a decision was made to investigate the illness on site.

According to Prof. Bo, four generations of the family were alive at the time, while another two generations were able to be traced back from elders' recollection. The team's research shows that among the 507 family members spanning six generations, 137 suffered loss of hearing during their childhood or adulthood. As the world became lonesome and pale after they went deaf, many people's personalities have undergone huge change.

During the preliminary stage of the research, molecular genetics was not as developed as it is today. However, after a number of years of study it was preliminarily established that the deafness in the family was genetic and passed on maternally. The length of the team's on-site research with the family is very rare by international standards.

The experts also discovered that the matrilineal relatives of this family were highly sensitive to aminoglycoside antibiotics, a form of antibiotic often administered into veins or muscle to treat serious bacterial infections such as gentamicin, kanamycin and streptomycin. A reasonable dose of an aminoglycoside has no harm to a normal person, but for the members of this family exposure could cause deafness.

Another interesting discovery from the research was that of a newly found double mutation of mtDNA peculiar to the genetic characteristics of the family.

The team's research indicates that the family is currently the largest family with reported hearing loss in the world.