Hemoglobin H hastalığında genetik danışmanlık önemli midir?

Alfa talasemi, α-globin zincirinin yetersiz ekspresyonu veya kesin yokluğu ile karakterize edilen genetik bir hastalıktır. Ülkemizde üç büyük delesyon (tal-1; 26.5 kb veya MedII, 20.5 kb ve 17.4 kb veya MedI) ve iki küçük delesyon (tal-2; 4.2 kb ve 3.7 kb) karakterize edilmiştir. Ayrıca α2-globin geninde (αα/αPAα), 5nt delesyonunda (αα/α5ntα) ve iki farklı PolyA mutasyonu (PA1: AATAAA>AATAAG ve PA2: AATAAA>AATGA) ve α1-globin geni (αα/αααCD59) tarafından sentezlenen kararsız Hb varyantı (CD 59; GGC→GAC) bildirilmiştir. α-thal-1 ve α-thal-2 (--/-α) veya nokta mutasyonlu (-/αPAα veya --/αααCD59) HbH genotiplerinin ondan fazla farklı kombinasyonu belirlenmiştir. Çukurova bölgesinde yapılan bu çalışmada alfa talasemi taşıyıcısı ailelere genetik danışmanlık verilmesinin öneminin vurgulanması ve genotip kombinasyonlarının belirlenmesi amaçlanmaktadır. Çukurova Üniversitesi Balcalı Hastanesi'ne başvuran ve kan sayımı sonucunda ağır anemi (Hb <9, MCV <70) tanısı alan 5 çocuk ve ailesinden alınan kan örneklerinden DNA izole edildi. HbA2 değerleri HPLC ile ölçüldü. Multipleks PCR ile gen delesyonları belirlendi. İki çocuklu iki aile karşılaştırıldığında, genetik danışmanlık hizmeti alan ailenin ikinci çocuğunun taşıyıcı, genetik danışmanlık hizmeti almayan ailenin ikinci çocuğunun ise hasta olması genetik danışma hizmetinin önemini vurgulamaktadıır.

Anahtar Kelimeler:

HbH, gen delesyonu, alfa talasemi

Is genetic counseling important in hemoglobin H disease?

Alpha thalassemia is a genetic disease characterized by insufficient expression or definite absence of the α-globin chain. Three large deletions (thal-1; 26.5 kb or MedII, 20.5 kb and 17.4 kb or MedI) and two small deletions (thal-2; 4.2 kb and 3.7 kb) have been characterized in our country. In addition, two different PolyA mutations (PA1: AATAAA>AATAAG and PA2: AATAAA>AATGA) on the α2-globin gene (αα/αPAα), 5nt deletion (αα/α5ntα), and unstable Hb variant (CD 59; GGC→GAC) synthesized by the α1-globin gene (αα/ααCD59) have been reported. More than ten different combinations of α-thal-1 and α-thal-2 (--/-α) or HbH genotypes with point mutations (--/αPAα or --/ααCD59) were determined. In this study, which was carried out in Çukurova region, it is aimed to emphasize the importance of giving genetic counseling to families with alpha thalassemia carriers and to determine genotype combinations. DNA was isolated from blood samples taken from 5 children and their families who were admitted to Çukurova University Balcalı Hospital and diagnosed with severe anemia (Hb <9, MCV <70) as a result of blood count HbA2 values were measured by HPLC. Gene deletions were determined by multiplex PCR. When two families with two children are compared, the fact that the second child of the family who receives genetic counseling service is a carrier and the second child of the family who does not receive genetic counseling service is patient highlights the importance of genetic counseling service.

Keywords:

HbH, alpha talassemia, gene deletion,

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