Two new sickle cell syndromes: HbS, Hb Camden, and alpha-thalassemia; and
HbS in combination with Hb Tacoma
GR Honig, RG Mason, M Shamsuddin, LN Vida, KR Rao and AR Patel
Hemoglobin variants having electrophoretic mobility more rapid than that of
HbA were identified in combination with sickle hemoglobin in two patients
at the Cook County Hospital. Neither individual had symptomatic hematologic
disease. In one patient, the rapidly migrating hemoglobin had the amino
acid substitution characteristic of Hb Tacoma (beta-40 arg leads to ser), a
mildly unstable variant. In the other patient, Hb Camden (beta-131 gln
leads to glu) was identified, and the hematologic findings also indicated
that he has alpha-thalassemia trait. In the patient with
HbS-Camden--alpha-thalassemia, globin synthesis was unbalanced (alpha/beta
0.66), and HbS represented only 19.5% of the total hemoglobin. The latter
finding suggests that under conditions of limited alpha-chain availability
beta Camden may combine with alpha subunits at least as efficiently as does
betaA. HbS represented 56% of the hemoglobin of the patient with HbS
Tacoma, although the rate of synthesis of beta Tacoma by her reticulocytes
was consistently greater than that of betaS. A time-course synthesis study
demonstrated a progressive increase in the specific activity of beta Tacoma
in relation to that of betaS, suggesting that the unstable beta- chains of
Hb Tacoma underwent selective intracellular degradation. This process
appears to explain the disparity between the rates of synthesis of the two
beta chains and the relative representation of HbS and Hb Tacoma in the
patient's erythrocytes.
Volume 55,
Issue 4,
pp. 655-660,
04/01/1980
Copyright © 1980 by The American Society of Hematology
