Journal of The Korean Society of Inherited Metabolic disease (대한유전성대사질환학회지)

The Korea Society of Inherited Metabolic Disease (대한유전성대사질환학회)
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Familial Glycogen Storage Disease Type IXa Diagnosed by Targeted Exome Sequencing

엑솜 시퀀싱으로 진단된 가족성 당원병 IXa 형 증례

  • Sohn, Young Bae (Department of Medical Genetics, Ajou University Hospital, Ajou University School of Medicine) ;
  • Jang, Ju Young (Department of Pediatrics, Ajou University Hospital, Ajou University School of Medicine) ;
  • Lee, Dakeun (Department of Pathology, Ajou University Hospital, Ajou University School of Medicine) ;
  • Jang, Ja-Hyun (Green Cross Genome)
  • 손영배 (아주대학교 의과대학 아주대학교병원 의학유전학과) ;
  • 장주영 (아주대학교 의과대학 아주대학교병원 소아청소년과) ;
  • 이다근 (아주대학교 의과대학 아주대학교병원 병리과) ;
  • 장자현 (녹십자지놈)
  • Published : 2017.12.30
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Abstract

Glycogen storage disease type IX (GSD IX) is caused by deficiency of phosphorylase kinase which plays a role in breakdown of glycogen. Mutations in PHKA2 are the most common cause of GSD IX (GSD IXa). Clinical manifestations of GSD IXa include hepatomegaly, elevation of liver enzyme, growth retardation, fasting hypoglycemia, and fasting ketosis. However, the symptoms overlap with those of other types of GSDs. Here, we report Korean familial cases with GSD IXa whose diagnosis was confirmed by targeted exome sequencing. A 4-year old male patient was presented with hepatomegaly and persistently elevated liver enzyme. Liver biopsy revealed swollen hepatocyte filled with glycogen storage, suggesting GSDs. Targeted exome sequencing was performed for the differential molecular diagnosis of various types of GSDs. A hemizygous mutation in PHKA2 were detected by targeted exome sequencing and confirmed by Sanger sequencing: c.3632C>T (p.Thr121Met), which was previously reported. The familial genetic analysis revealed that his mother was heterozygous carrier of c.3632C>T mutation and his 28-month old brother had hemizygous mutation. His brother also had hepatomegaly and elevated liver enzyme. The hypoglycemia was prevented by frequent meals with complex carbohydrate, as well as cornstarch supplements. Their growth and development is in normal range. We suggest that targeted exome sequencing could be a useful diagnostic tool for the genetically heterogeneous and clinically indistinguishable GSDs. A precise molecular diagnosis of GSD can provide appropriate therapy and genetic counseling for the family.

당원병 IX형은 phosphorylase kinase 효소 결핍으로 분해되지 않은 당원이 간 또는 근육에 축적되는 유전성대사이상질환이다. 당원병 IXa형은 당원병 IX형 중 가장 흔한 형태로 PHKA2 유전자 변이로 발생한다. 당원병 IXa형의 임상증상은 간 비대, 간 효소 수치 상승, 성장 지연, 저혈당 등이 있다. 그러나, 이러한 임상 증상은 다른 타입의 당원병의 증상과 비슷하거나 겹쳐서 임상적으로는 구분하기가 어렵다. 저자들은 표적 엑솜 시퀀싱으로 진단된 가족성 당원병 IXa형 증례를 보고하고자 한다. 4세 남아가 간 비대와 간 효소 수치 상승을 주소로 내원하였다. 간 조직검사결과 간세포에 당원이 축적되어 있어 당원병을 의심하였으나 G6PC 유전자 검사는 음성이었다. 이에 당원병 타입을 감별진단 하기 위해 표적 엑솜시퀀싱을 시행하였으며, PHKA2 유전자에서 질환과의 연관성이 이미 보고된 바 있는 c.3632C>T (p.Thr121Met) 변이가 반접합체(hemizygote)로 발견되어 당원병 IXa로 진단하였다. 가족 유전자 검사를 통해 어머니가 이형접합체 보인자임을 확인하였으며, 남동생이 같은 변이를 가진 반접합체임을 확인하였다. 28개월 된 환자의 남동생 역시 신체 검진 상 간 비대가 있었으며, 혈액검사상 간 효소 수치가 상승되어 있어 같은 질환으로 확진하였다. 이환된 형제 모두 생 옥수수 전분 섭취와 복합 탄수화물을 섭취하도록 식이 조절을 하였으며 2년 추적관찰 동안 정상 성장 발달을 보이고 있다. 당원병과 같이 임상적으로 구분이 어려우며 유전학적으로 다양한 유전자 변이를 보이는 당원병과 같은 질환의 분자 유전학적 감별진단에 표적 엑솜 시퀀싱이 유용한 진단법이 될 수 있다. 신속하고 정확한 분자 유전학적 감별진단을 통해 환자와 보호자에게 질병의 적절한 치료법, 질병의 예후에 관한 정확한 정보를 제공할 수 있을 뿐 아니라, 적절한 유전상담을 제공할 수 있다.

Keywords

References

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