Clinical and Experimental Pediatrics

The Korean Pediatric Society (대한소아청소년과학회)
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A case of two sisters births from mother with phenylketonuria lacking mental retardation

정신 지체가 아닌 페닐케톤뇨증 산모에서 출생한 자매 1례

  • Ki, Chang-Seok (Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sung Kyun Kwan University School of Medicine) ;
  • Kim, Jin Kyung (Department of Pediatrics, College of Medicine, Daegu Catholic University)
  • 기창석 (성균관대학교 의과대학 삼성서울병원 진단검사의학교실) ;
  • 김진경 (대구가톨릭대학교 의과대학 소아과학교실)
  • Received : 2007.12.19
  • Accepted : 2008.03.11
  • Published : 2008.05.15
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Abstract

In this untreated classic phenylketonuria (PKU) case, mental retardation is severe; however, there have been individuals- like the mother of this case- who have escaped mental retardation and all the other potential sequelae of phenylketonuria, despite having high blood phenylalanine levels, and very poor dietary control. It appears that they have nearly normal brain phenylalanine levels despite high blood phenylalanine (Phe) levels. A number of studies have now demonstrated considerable variability in blood vs. brain phenylalanine levels in phenylketonuria patients. Outcome of phenylketonuria appears to be related to brain phenylalanine levels. We report a case of "undiagnosed" maternal phenylketonuria syndrome. A female infant had low birth weight (2,400 g) with microcephaly. We examined her family and discovered that her mother was an undiagnosed phenylketonuria patient with a borderline intelligence quotient (IQ). The infant's sister, six years old, was diagnosed with phenylketonuria at the age of four years was mentally retarded and had received an operation for cleft lip and palate. the sister had also had a low birth weight (2,300 g). Her sister and mother were compound heterozygotes (mother: R243Q/Y325X; sister: Y325X/P407S). The infant and father were heterozygous carriers (baby: R243Q/ -; father: P407S/ - ).

전형적 페닐케톤뇨증에서 식이 요법을 조기에 실시하지 않으면 생후 1세경에는 지능 지수가 50이하로 심한 정신지체가 된다고 알려져 있으나, 일부에서는 심한 정신 지체를 보이지 않기도 한다. 그 기전은 확실치 않으나 혈장에서보다는 뇌에서의 페닐알라닌 수치와 관련이 있을 것으로 생각되고 있다. 또한 페닐케톤뇨증 여성이 임신을 한 후 식이조절에 실패하게 되면 증가된 혈중 페닐알라닌이 태아에 영향을 주어 출생 후 저체중, 소두증, 선천성 심질환, 발달 지연, 지능 저하, 등이 올 수 있다. 따라서 전체 임신 기간 중 산모의 혈장 내 페닐알라닌을 6 mg/dL 미만으로 유지하도록 조절하여야 한다. 본 증례의 산모는 정신 지체는 아니었으므로, 본인이 페닐케톤뇨증 환자인지 모르고 지내다가 두 자녀를 출산하였다. 첫째아이는 4세경에 타병원에서 페닐케톤뇨증으로 진단받았으며, 저출생체중과 구개열의 수술병력 및 소두증이 있었다. 둘째아이는 페닐케톤뇨증은 아니었으나, 저출생체중과 소두증, 및 발달 지연을 보이고 있다. PAH유전자 분석에서 환아의 어머니는 R243Q/Y325X, 환아의 언니는 Y325X/P407S로 compound heterozygotes 임을 확인하였다. 환아의 아버지와 환아는 각각 P407S/- 및 R243Q/-를 가진 heterozygous 보인자이었다. 따라서 페닐케톤뇨증 환자 중 일부에서는 심한 정신 지체는 없이 일상적인 생활을 하는 경우도 있으므로, 출생아에서 원인이 밝혀지지 않는 저체중, 소두증, 지능 발달 지연 등이 있을 때는 가족력을 확인해 볼 필요가 있다.

Keywords

References

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