In affected members of a large consanguineous Tunisian family with Usher syndrome type IIC (USH2C; 605472 ), Hmani-Aifa et al. (2009) identified a homozygous 18131A-G transition in exon 85 of the GPR98 gene, resulting in a tyr6044-to-cys (Y6044C) substitution in a highly conserved residue in the second extracellular loop. The mutation was predicted to disrupt an interloop disulfide bridge, leading to an improperly folded loop and nonfunctional receptor. Heterozygous mutation carriers were unaffected. The family also segregated nonsyndromic retinitis pigmentosa-40 (RP40; 613801 ), caused by a homozygous mutation in the PDE6B gene ( ). One family member who was doubly homozygous for both mutations had a more severe ocular phenotype. Two family members who were doubly heterozygous for both mutations were unaffected at ages 82 and 65 years, respectively. Hmani-Aifa et al. (2009) commented that consanguinity can increase familial clustering of multiple hereditary diseases within the same family. The family had originally been reported by Hmani et al. (1999) .
Francoise Bachelerie, Adit Ben-Baruch, Israel F. Charo, Christophe Combadiere, Joshua M. Farber, Reinhold Förster, Gerard J. Graham, Richard Horuk, Massimo Locati, Andrew D. Luster, Alberto Mantovani, Georgios L Moschovakis, Philip M. Murphy, Robert J. B. Nibbs, Hisayuki Nomiyama, Joost J. Oppenheim, Christine A. Power, Amanda E. I. Proudfoot , Mette M. Rosenkilde, Antal Rot, Silvano Sozzani, Marcus Thelen, Osamu Yoshie, Albert Zlotnik. Chemokine receptors. Accessed on 20/10/2017. IUPHAR/BPS Guide to PHARMACOLOGY, http:///GRAC/FamilyDisplayForward?familyId=14 .