Hematological evaluation of patients with various combinations of α-thalassemia

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Abstract
Six patients and their parents from five different families with Hb H have been evaluated clinically and hematologically. Previous studies using restriction endo‐nuclease mapping technique indicated that α‐thalassemia determinants in these cases are heterogeneous. Only one of the five cases have the usual genotype for Hb H, which is characterized by an α‐DNA‐specific fragment of 20 kb long by Eco RI digestion. Three cases from two different families have Hb H disease with α‐specific DNA fragments of 22.5 kb/2.6 kb long; and the other two have α‐specific DNA fragments of 20 kb/2.6 kb long, in Eco RI digestion of the cellular DNA. The hematological examination of the parents suggests that the α‐thalassemia condition associated with the Eco RI fragment of α‐specific cellular DNA of approximately 22.5 kb long produces an α‐thal‐2‐like clinical condition, while the other α‐thalassemia determinant associated with a fragment 2.6 kb long results in an α‐thal‐1‐like clinical condition. The clinical and hematological findings of the cases with 22.5 kb/2.6 kb fragment patterns were more severe than the case with the 20 kb/2.6 kb combination. This study suggests that variation in the clinical and hematological findings among patients with Hb H disease may well reflect a heterogeneity of the genotypic combination.