|Year : 1982 | Volume
| Issue : 1 | Page : 1-3
Genotypic analysis of symptomatic thalassemia syndromes (A study of 292 unrelated cases from Bombay).
MB Agarwal, BC Mehta
M B Agarwal
|How to cite this article:|
Agarwal M B, Mehta B C. Genotypic analysis of symptomatic thalassemia syndromes (A study of 292 unrelated cases from Bombay). J Postgrad Med 1982;28:1-3
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Agarwal M B, Mehta B C. Genotypic analysis of symptomatic thalassemia syndromes (A study of 292 unrelated cases from Bombay). J Postgrad Med [serial online] 1982 [cited 2022 May 21 ];28:1-3
Available from: https://www.jpgmonline.com/text.asp?1982/28/1/1/5614
Thalassemia is the commonest of all the inherited hemolytic anemias seen in India. Though the earliest case was described in 1925, it was only after 1940, that the genetic variants of this disorder were appreciated. Thalassemia results from decreased synthesis of one or more of the globin chains. Being an autosomal co dominant disorder, it could present both in the heterozygous or homozygous form. Moreover, complex situations arise due to interaction between different thalassemia genes or from interaction of a thalassemia gene with that for an abnormal hemoglobin. Such variations can only be diagnosed by parents' study.
As the natural history and the problems of various thalassemic syndromes differ, it would be of interest to the physicians dealing with such cases to be aware of their genotypic distribution in a given population. Hence 292 unrelated cases of thalassemic syndrome diagnosed at our clinic over the last 8 years for one or other symptoms were studied and classified genotypically.
MATERIAL AND METHODS
Thalassemia was diagnosed when cases of anemia had an elevated level of Hb F and/or Hb A2 or an abnormal Hb like Hb H, Hb Lepore or Hb constant spring. Standard techniques were used for the estimation of Hb F and Hb electrophoresis as described by Dacie and Lewis. Parents were studied to detect the nature of thalassemia genes and/or the abnormal Hb involved. The hematological criteria used for the diagnosis of different genotypes are shown in[Table 1.]
The 292 cases of thalassemia syndromes showed a variable genetic picture as shown in [Table 2.]
The thalassemia syndrome forms one of the most fascinating subjects for a student of Genetic Hematology. Although, commonly it is a result of diminished betachain production, a large number of variations are known. These include Delta-beta thalassemia, Hb H disorder, HPFH, Hb Lepore and Hb constant spring. In addition, there are a number of extremely rare sub-types which can only be diagnosed with difficulties e.g. Gamma-thalassemia. Lastly, any abnormal hemoglobin (structural variant) can interact with a thalassemic gene.
As seen in [Table 2], beta-thalassemia forms a very common problem. It was responsible for 97.2% of cases in the present group. Delta-beta thalassemia and HPHF are rare but equally important as on interaction with beta-thalassemia they result in disorders of intermediate severity [Table ]. Such intermediate disorders may often go undiagnosed as they produce vague symptoms or signs like hepatosplenomegaly, stunted growth, refractory anaemia or recurrent jaundice.
Hb H disease is uncommon in India. Only two cases (0.7%) were seen in the present study. Interestingly, Hb constant spring, which has an incidence as that of Hb H disorder in the South East Asia, has never been reported from India. We also did not encounter any case of Hb constant spring or even Hb Lepore in the present study.
Any abnormal Hb with an altered betachain structure can produce a significant hemolysis on interaction with beta-thalassemia gene. Once again, the clinical severity is variable [Table 2]. The incidence of such syndromes depends on the prevalence of the abnormal Hb in a given population. In the present study, Hb-S thalassemia and Hb-E thalassemia formed the commonest problem i.e. 9.8% and 4.0% respectively. Hb-E thalassemia is said to be as common as homozygous betathalassemia in Bengal i.e. Eastern part of India. Similarly Hb S thalassemia is present with a higher incidence than homozygous beta-thalassemia in tribal communities of Madhya Pradesh i.e. Central India. Lastly Hb-D thalassemia which formed only 1.3% of the present group is seen much more commonly in Punjabis and Sikhs belonging to the Northern States of India. Another factor which affects the incidence of Hb D thalassemia in a clinical series like ours, is the relatively asymptomatic nature of this disorder. Any study based on population survey has much higher incidence of Hb D thalassemia even in Bombay.
We are thankful to Dr. C. K. Deshpande, Dean, Seth G.S. Medical College and K.E.M. Hospital for permitting us to use this hospital data.
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