Hb S Mobile: a new genetic combination.

The genetic combination of Hb Mobile (beta 73 Asp replaced by Val) and Hb S (beta 6 Glu replaced by Val) was found in a healthy black man whose hemolysate resembles that of Hb S electrophoretically. His mother and sister have Hb AS; the father and brother have Hb A Mobile. No clinical nor hematologic abnormalities were detected in any member of the family. A slightly decreased oxygen affinity associated with Hb Mobile appears to have no clinical significance. Simple methods of differentiating Hb Mobile S from the electrophoretically similar but clinically severe Hb SD Los Angeles are described.