Escher Hirt syndrome
Overview
Escher-Hirt syndrome: A very rare syndrome characterized by thick earlobes and conductive deafness due to an inner ear structure abnormality. The deafness is non-progressive and occurs at birth.
Symptoms
* Conductive deafness * Middle ear abnormality * Small jaw
Causes
Genetic causes account for 30-50% of hearing losses and can be divided into syndromic and nonsyndromic types. As with all genetic syndromes, genetic causes of hearing loss may be autosomal dominant (AD), autosomal recessive (AR), X-linked, or sporadic. Nonsyndromic deafness accounts for slightly more than half of all cases of genetic deafness. It probably accounts for most cases classified as unknown. Children with nonsyndromic deafness are deaf or hard of hearing; however, they have no other physical abnormalities, no particular risk to other organ systems, and no increased risk of mental deficiency. Some children have a history of deafness in a close or distant family member. Others have new mutations or an AR gene with no known proband. The histories of subsequent siblings and progeny may help to distinguish a genetic cause from developmental arrest or a prenatal insult. Exciting developments in genetic mapping have revealed approximately 2 dozen abnormal genes that lead to deafness. In some, the molecular or structural defect has been identified (eg, collagen in the basilar membrane, structural defect in a membrane-gating protein). These genes have been classified according to their mode of inheritance: ADs (DFNA1 through DFNA11), ARs(DFNB1 through DFNB12), X-linked recessives (DFN1 through DFN6), or mitochondrial (12Sr RNA and tRNA-Ser UCN). Some of the genes exhibit variable penetrance.
Diagnosis
Differential diagnosis with other genetic syndromes associated with deafness, and possible therapeutic approaches are discussed.