Early onset sensorineural hearing loss: association studies with major histocompatibility class III (complement) markers.

: In 39 families with at least one child suffering from moderate or severe bilateral sensorineural hearing loss (SNHL), major histocompatibility complex (MHC) class III complement phenotypes were retrospectively determined by standard methods; MHC class I segregation data was also available. The families were treated in the Hospital for Communication Disorders and selected for the HLA-B16 and B18 specificities, respectively. Haplotype and allele frequencies were derived from segregation analysis in the families. From 31 unrelated children with random and familiar forms of SNHL significant deviations in the distribution were seen for the following MHC class III alleles using as a control population 60 German healthy individuals: duplicated C4A alleles (C4"DA") p = 0.009, silent C4A alleles (C4A*Q0) p = 0.006, duplicated heavy C4 beta-chain alleles (C4 beta"DHH") p = 0.0003, and silent C4 beta-chain alleles (C4 beta*Q0) p = 0.0075. In serum samples from patients with an assumed genetic disposition according to clinical criteria indications for an association were found for C4"DA" (p = 0.03), C4A*Q0 (p = 0.003), C4B*3 (p = 0.046), C4 beta"DHH" (p = 0.004), and C4 beta*Q0 (p = 0.02). The underrepresentation of C4A*Q0 may be an indicator for aberrant or duplicated C4 alleles on the same haplotype or exhibit a protection mechanism for acquiring the inheritable forms of early onset SNHL.