APA (Old Order Amish; Eastern Pennsylvania)
MEN (General Swiss-German Mennonite)

Inheritance: autosomal recessive
autosomal dominant
x-linked
Genes: GJB2

Neurosensory non-syndromic recessive deafness I
NSRD1

Hearing loss
Neurosensory deafness

Deafness, Non-Syndromic Recessive

Clinical Characteristics

General description (for patients):

There are many types and causes of deafness but this one is hereditary and involves the neural pathways.  Onset is evident early with some hearing deficit present at birth and is progressive throughout childhood. There are at least two types in plain people in Eastern Pennsylvania, one among Mennonites and another among Amish. High-pitched sounds are lost first, followed by low-pitched ones.

Medical description:  

Many types of hereditary hearing loss have been reported and studied.  Even among the type described here, non-syndromic, neurosensory and recessively inherited, there are several types.  This one is congenital and mild at birth but hearing loss is progressive in childhood.  Early enrollment in deaf education programs is beneficial for neuromotor development even though there is no evidence that other systems are involved.  At least two forms exist among plain people in Eastern Pennsylvania.

Genetics:

About half of deafness cases are due to genetic mutations of which there are more than 50.  Of these, 60-70% are non-syndromal, caused by isolated mutations.  The remainder are due to syndromal mutations that also cause defects in other organs and systems.  Non-syndromic mutations may be inherited in autosomal recessive, autosomal dominant and X-linked patterns secondary to mutations in at least 70 mapped genes.  More than 20 of these have been identified and characterized.  Among the Amish and Mennonites of Eastern Pennsylvania there are at least two recessive forms of early-onset neurosensory hearing loss as evidenced by the fact that a deaf Amish individual married a deaf Mennonite and they had hearing offspring.
The mutated locus for at least one of these types in Pennsylvania is on chromosome 13 (13q11-q12) in a gene known as GJB2, where a deletion (35delG) has been found.  This deletion accounts for the majority of mutations in this gene encoding connexin-26 (CX26) which are responsible for at least 50% of non-syndromal recessive deafness throughout the world.

Treatment:

None known.

Prognosis:

Permanent hearing loss only.

Ancillary treatments and support:

Special education in school for the deaf.

Specialists and specialty centers:

Otolaryngologist.

References:

Mengel, M.C., Konigsmark, B.W., Berlin, C.I., and McKusick, V.A.:  Recessive early-onset neural deafness.  Acta Otolaryngol. 64: 313-326, 1967.  PubMed ID: 6077778

Petersen, M.B., and Willems, P.J.:  Non-syndromic, autosomal-recessive deafness.  Clin. Genet. 69: 371-392, 2006.  PubMed ID:16650073

Mengel, M.C., Konigsmark, B.W., and McKusick, V.A.:  Two types of congenital recessive deafness. In: Medical Genetic Studies of the Amish.  Johns Hopkins Press, Baltimore, MD. Pp. 138-142, 1978. (See also Eye, Ear, Nose, Throat Monthly 48: 301-305. 1969. PubMed ID: 5779514).

Tekin, M., Amos, K.S. and Pandya A.:   Advances in hereditary deafness.  Lancet 358: 1082-1090, 2001. PubMed ID: 11589958