TYPE | HPFH-2; Ghanaian (see Fig. 13) | ||
---|---|---|---|
CAUSE | A very large deletion of ~105 kb long extending from the IVS-II of the psibeta gene to ~90 kb downstream from the 3' end of the psibeta gene. The exact 5' breakpoint is at position IVS-II-51 of the psibeta gene. The 3' breakpoint is mapped to an L1 family repeat, located outside the sequence region of the beta-globin gene cluster. | ||
DETECTION | Gene mapping and sequencing. The Ggamma-globin gene does not carry the C->T mutation resulting in lower Ggamma values. | ||
PHENOTYPE | This is similar to that of HPFH-1. Heterozygotes have a normal hematology with Hb F levels averaging 24.4±2.8% (n=56) with an average Ggamma value of 32.3±4.8%. The level of Hb A2 is decreased. Homozygotes have a mild erythrocytosis (Hb 15.5-18.0 g/dl) with 100% Hb F and Ggamma values of 45-60%. | ||
DISTRIBUTION | In Black families from Africa and the Americas. First observed among Ghanaian families. |
REFERENCES | |||
1. | Ringelhann, B., Acquaye, C.T.A., Oldham, J.H., Konotey-Ahulu, F.I.D., Yawson, G., Sukumaran, P.K., Schroeder, W.A., and Huisman, T.H.J.: Biochem. Genet., 15:1083, 1977. | ||
2. | Tuan, D., Feingold, E., Newman, M., Weissman, S.M., and Forget, B.G.: Proc. Natl. Acad. Sci. USA, 80:6937, 1983. | ||
3. | Kutlar, A., Gardiner, M.B., Headlee, M.G., Reese, A.L., Cleek, M.P., Nagle, S., Sukumaran, P.K., and Huisman, T.H.J.: Biochem. Genet., 22:21, 1984. | ||
4. | Collins, F.S., Cole, J.L., Lockwood, W.K., and Iannuzzi, M.C.: Blood, 70:1797, 1987. | ||
5. | Bakioglu, I., Kutlar, A., and Huisman, T.H.J.: Biochem. Genet., 24:149, 1986. |