Hb O-Tibesti [beta121(GH4)Glu-->Lys; beta11(A8)Val-->Ile], a hemoglobin variant carrying in the same beta chain the substitutions of Hb O-Arab and Hb Hamilton, found in combination with Hb S [beta6(A3)Glu-->Val].

Hb O-Tibesti, carries in the same chain the substitution of Hb O-Arab [beta121(GH4)Glu-->Lys] and that of Hb Hamilton [beta11(A8)Val-->Ile]. Hb O-Tibesti may be distinguished from Hb O-Arab by polyacrylamide gel electrophoresis in the presence of urea and Triton-X100, and by reversed phase high performance liquid chromatography. It was found in a compound heterozygous condition with Hb S [beta6(A3)Glu-->Val] in a child of Chad-Sudanese descent, suffering from a sickle cell syndrome. Compared to the classical description of the Hb S/Hb O-Arab association, the additional Hb Hamilton mutation does not seem to modify the clinical presentation.