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

The Korea Society of Inherited Metabolic Disease (대한유전성대사질환학회)
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Ten Cases of R53H Variant of PAH Gene in Benign Hyperphenylalaninemia

PAH 유전자의 R53H 유전자변이를 보인 양성 고페닐알라닌혈증 10례

  • Lee, Jiyun (Department of Pediatrics, Soonchunhyang University Hospital Seoul, Soonchunhyang University College of Medicine) ;
  • Lee, Jeongho (Department of Pediatrics, Soonchunhyang University Hospital Seoul, Soonchunhyang University College of Medicine) ;
  • Lee, Dong Hwan (Department of Pediatrics, Soonchunhyang University Hospital Seoul, Soonchunhyang University College of Medicine)
  • 이지윤 (순천향대학교 의과대학 소아과학교실) ;
  • 이정호 (순천향대학교 의과대학 소아과학교실) ;
  • 이동환 (순천향대학교 의과대학 소아과학교실)
  • Published : 2017.04.30
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Abstract

Purpose: Phenylketonuria (PKU) results from a deficiency of phenylalanine hydroxylase (PAH). The mutation of the PAH gene results in decreased phenylalanine hydroxylase enzyme activity in hyperphenylalaninemia (HPA) patients. This study reports ten cases of patients with the benign HPA genotype c.158G>A (p.Arg53His, R53H) variant in the PAH gene and aims to evaluate the clinical significance of the R53H variant. Methods: Ten Korean patients with the HPA genotype the R53H variant were included in this study. A retrospective medical record review was conducted. We characterized the phenotypes of the patients with HPA with the R53H variant using the following system: classic PKU, moderate PKU, mild PKU, Mild HPA, and benign HPA. Results: Five patients had the R53H variant with the "Pathogenic" variants (R413P, R241C, $Y356^*$, c.442-1G>A, $Y325^*$), Two patients had the "Likely pathogenic" variants ($W187^*$, A259T), Two patients had the "Uncertain significance" variants (R53H, G344D), and One patient had the "Not provided" variant (c.1066-14C>G). Nine patients genotyped with the R53H variant were the patient with benign HPA and One patient genotyped with the R53H homozygote was within normal range of plasma phenylalanine. None of the ten patients required dietary restriction of phenylalanine or pharmacotherapy to maintain their plasma phenylalanine levels and showed no clinical symptoms of HPA. Conclusion: Ten patients with HPA genotype the R53H variant were the patient with benign HPA and showed no clinical symptoms of HPA. Thus, the R53H variant, which was previously classified as an "Uncertain significance" mutation in HPA patients, should be re-classified as "Benign."

서론: 페닐케톤뇨증은 방향족 아미노산의 하나인 페닐알라닌의 대사장애가 발생하는 유전성 대사질환이다. 양성 고페닐알라닌혈증은 페닐알라닌 수산화효소(PAH) 유전자 변이가 발견되는 페닐케톤뇨증 환자에서 저페닐알라닌 식사 치료가 필요 없이 정상적인 성장 및 발달이 가능한 질환이다. 최근 PAH 유전자의 R53H 변이는 병적이라기 보다 양성에 가까운 것으로 생각되었으며 저자들은 양성 고페닐알라닌혈증 환자들에서 R53H 유전자변이를 보인 10례를 경험하였기에 보고하는 바이다. 방법: 2010년 4월부터 2017년 5월까지 순천향대학교 서울병원에서 추적관찰하고 있는 양성 고페닐알라닌혈증 환자 중 R53H변이를 가진 10명의 한국인 환자의 의무기록을 검토하였다. 환자들은 혈중 아미노산 분석을 통해 고페닐알라닌혈증을 진단받았으며, 모든 환자들은 PAH 유전자 검사를 통해 유전자 변이를 진단받았다. 환자들의 의무기록 검토를 통해 환자의 동반 유전자 변이, 증상 및 혈중 페닐알라닌 농도, 치료여부 등을 분석하였다. 결과: 상기 환자들 중 5명은 R53H와 함께 "병적인" 유전자를 보였으며(R413P, R241C, $Y356^*$, c.442-1G>A, $Y325^*$), 2명에서는 "병적일 수 있는" 유전자 변이를 보였다($W187^*$, A259T). "중요도가 확실하지 않은" 유전자 변이를 가진 환자는 2명이었으며(R53H, G344D), 이 중 35세 남성 1명은 R53H의 동형접합자였다. 1명의 환자에서는 아직 밝혀지지 않은 인트론(intron) 변이가 발견 되었다. 환자들은 혈중 페닐알라닌 수치가 $103.1{\mu}mol/L$ 였던 R53H 동형접합체인 35세 남자 환자를 제외하고는 모두 양성 고페닐알라닌혈증으로 진단되었다. 모든 환자에서 정상 식사를 진행하였으며, 약물 치료는 시행하지 않았다. 모든 환자에서 페닐케톤뇨증의 증상은 없었다. 결론: 본 연구의 R53H 유전자 변이를 가진 환자 10명은 특별한 치료 없이도 정상적인 성장 및 발달을 보였다. 이는 이전에 양성 고페닐알라닌혈증으로 진단된 환자들의 R53H 변이가 정상 변이일 가능성이 높음을 의미하는 것이며 이형접합으로 병적변이를 가진 사람들이 환자가 아니라 보인자 또는 정상인일 수 있음을 의미한다. 따라서 현재 "중요도가 확실하지 않은"으로 분류되어있는 R53H변이는 "양성"으로 분류되어야 할 것이다.

Keywords

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