**2.5 Signs**

HL may be associated with other physical problems which are called syndromic HL. Genetic HLs without any other complications is called non-syndromic genetic hearing loss [Willems, 2004]. HL loci are named with the prefix DFN, followed by the mode of inheritance which is indicated by B, A, X and Y for autosomal recessive (DFNB), autosomal dominant (DFNA), X-linked (DFNX) and Y-linked (DFNY), respectively. The order in which loci have been described is denoted by a number after these letters, e.g. DFNB1 is the first identified locus causing autosomal recessive HL [Guilford et al., 1994].


Table 2. Various criteria for the classification of hearing loss.
