一例稀有型地中海贫血患者的家系鉴定分析

Identification of a Rare Unknown Genotype Thalassemia Proband and His Family Members

目的:通过对发现的一例未知基因型的地中海贫血表型患者的家系进行鉴定,研究稀有地贫临床上的检测方法,为稀有型地贫患者的诊断提供方法,及时干预.方法:对先证者及其父、母、妻、子进行血液学检测,同时采用聚合酶链反应-反向点杂交法(PCR-RDB)和裂口PCR法(Gap-PCR)分别检测该家系常见的地贫基因和稀有型地贫基因,分析该家系的地贫结果.结果:先证者的常见地贫基因正常,但经Gap-PCR检测地贫基因为东南亚缺失型β-地中海贫血(SEA-HFPH);其父和其妻的血液学和基因检测结果均正常;而其母和其子的血液学检测结果显示,他们除血红蛋白A2 (HbA2)轻度增高,血红蛋白F(HbF)没有明显增高,平均红细胞体积(MCV)和平均红细胞含量(MCH)水平降低,呈现小细胞低色素性贫血,常见地贫基因检测正常,稀有地贫基因检测为HFPH阳性.结论:常见地贫基因检测方法即PCR-RDB无法检出稀有型地贫,因此建议临床上结合血液学检测与Gap-PCR两种方法,全面诊断稀有型的地贫,而不以常见地贫基因检测结果作为唯一诊断标准,以防止地贫的漏检和误检,真正做到有效产前诊断.

A research has been study through a case of unknown genotype thalassemia,with exploring the process of screening and authenticating his extended family members,in order to reduce the misdiagnosis rate of rare thalassemia by applying appropriate clinical test method.Methods:Hematological examination,PCR-RDB and Gap-PCR were performed at the same time for the proband and his father,mother,wife and son in order to analysis this genealogical thalassemia result.Result:Proband’s ordinary gene screening of thalassemia turned out to be normal,while Gap-PCR indicatedβ-thalassemia deletion about Southeast Asian,which was known by hereditary persistence of fetal hemoglobin about Southeast Asian(SEA-HPFH).All examinational results of his father and wife were normal.While results of proband’s mother and son showed difference.Apart from HbA2 increased slightly,HbF were not apparently increased,and screening of ordinary gene of thalassemia showed normal.Not only the MCV and MCH levels were decreased,which meant Microcytic hypochromic anemia,the screening of rare fene of thalassemia showed positive in HPFH,therefore result indicated SEA-HPFH.Conclusion:PCR-RDB indicated that rare thalassemia can be misdiagnosed,which common standard can’t check out the rare.Therefor we suggest clinical screening of thalassemia to combine routine hematologic examination and common standard,even with Gap-PCR to diagnosis whether it concerns rare genotype thalassemia or not,rather than rely only on the result of common genotype thalassemia test as the best standard to identify thalassemia.Which can help protect misdiagnosis and doing well in prenatal diagnosis.