Many inborn errors of metabolism can be completely cured with early detection and early treatment. This is why neonatal screening on inborn errors of metabolism is implemented worldwide. In 1991, the Ministry of Health & Social affairs adopted a nationwide service program for neonatal screening of phenylketonuria, galactosemia, maple syrup urine disease, homocystinuria, histidinemia and congenital hypothyroidism for newborns delivered from low class pregnant women registered in health centers. Government decreased the test items from six to two, PKU and congenital hypothyroidism to increase test numbers with same budget from 1995. 78 laboratories wanted to participate for neonatal screening test in 1999. Government decided to screen six items of PKU, congenital hypothyroidism, maple syrup urine disease, homocystinuria, galactosemia and congenital adrenal hyperplasia from 2006. In 2014, thirteen laboratories are participating. Inter laboratory quality control was started 6 times a year from 1994. In case a patient with an inherited metabolic disease is diagnosed by screening of government program, special milk is provided at government's expense. According to the government project, from 1997 to 2013, 7,080,569 newborns were screened. 144 PKU, 2.451 congenital hypothyroidism were detected. So incidence of PKU is 1/49,170 and congenital hypothyroidism is 1/2,888. The cost benefit of performing screening procedures coupled with treatment has been estimated to be as high as 1.77 times in PKU, 11.11 times in congenital hypothyroidism than cost without screening. By January 2007, many European countries had expanded of their newborn screening programs by inclusion of Tandem mass spectrometry. We are trying to increase the budget to test all newborns for Tandem mass spectrometry from 2016. We are considering four to five central laboratories which cover all newborns and are equipped with tandem mass spectrometer & enzyme immunoassay for TSH, 17OHP & enzyme colorimetric assay for galactose. And I hope to expand test including Wilson disease screening test and lysosomal storage diseases.

Recent advances in the diagnosis and treatment of inborn errors of metabolism have improved substantially the prognosis of many of these diseases, if diagnosed early enough before irreversible damage occurs. This makes it essential that the practicing pediatrician, especially neonatologists be familliar with the clinical presentations and systematic approaches of these disorders. Characteristic clinical presentations, methods of systematic approach and typing of various disorders is discussed in this review. The signs of neurological dysfunctions of many IEMs manifesting in the neonatal period is very nonspecific, such as poor feeding, poor sucking, apnea or tachypnea, vomiting, hypertonia, hypotonia, seizure, letharginess, consciousness change and coma. Many other non-metabolic severe disorders of neonatal period such as neonatal sepsis and intracerebral hemorrhage share these nonspecific symptoms. Hyperammonemia, metabolic acidosis, ketosis and hyperlatic acidemia are observed in many of these conditions but there are exceptions in which conditions all basal laboratory tests are normal, such as NKH, sulfite oxidase deficiency and peroxisomal disorders. According to the results of basal laboratory tests, IEMs in the neonatal period can be categorized in to 6 types. Grouping of IEMs into 6 types will make confirmatory tests and early emergency treatment more efficient.

Mucopolysaccharidoses (MPSs) are a group of rare inherited metabolic diseases caused by deficiency of lysosomal enzymes. MPSs are clinically heterogeneous and characterized by progressive deterioration in visceral, skeletal and neurological functions. The aim of this article is to review the treatment of MPSs, the unmet needs of current treatments and vision for the future including recent clinical trials. Until recently, supportive care was the only option available for the management of MPSs. Hematopoietic stem cell transplantation (HSCT), another potentially curative treatment, is not routinely advocated in clinical practice due to its high risk profile and lack of evidence for efficacy. From the early 2000s, enzyme replacement therapy (ERT) was approved and available for the treatment of MPS I, II and VI. ERT is effective for the treatment of many somatic symptoms, particularly walking ability and respiratory function, and remains the mainstay of MPS treatment. However, no benefit was found in the neurological symptoms because the enzymes do not readily cross the blood-brain barrier (BBB). In recent years, intrathecal (IT) ERT, substrate reduction therapy (SRT) and gene therapy have been rapidly gaining greater recognition as potential therapeutic avenues. Although still under investigation, IT ERT, SRT and gene therapy are promising MPS treatments that may prevent the neurodegeneration not improved by ERT.

Fabry disease is an X-linked disease caused by deficiency of the lysosomal enzyme alpha-galactosidase A. Affected males present anhydrosis, acroparesthesia and angiokeratoma, and subsequently cardiac, cerebral and renal complications are followed. Females and atypical variants show heterogeneous clinical symptoms. In 2001, two recombinant enzymes were approved for Fabry disease: agalsidase alpha and agalsidase beta. Since the introduction of enzyme replacement therapy (ERT), the number of long-term follow-up studies has been reported. Long-term ERT showed effectiveness on renal function in patients with chronic kidney disease, decrease or stabilization of left ventricular mass, and improvement of pain and quality of life. However, there were limited effects on cerebrovascular events and their mortality. Current literatures on the clinical effect of ERT have reported limited datain adult patients who have already advanced disease. Therefore, further study for pre-symptomatic patients and atypical variants is needed to verify the impact of ERT. This review summarized recent progresses in ERT and limitations of long-term effect of ERT in patients with Fabry disease.

Gaucher disease is a multisystemic disorder arising from a deficient activity of the lysosomal enzyme glucocerebrosidase, which leads to accumulation of glycosylceraide and other glycolipids in the regiculoendothelial system. The characteristics of Gaucher disease are anemia, thrombocytopenia, hepatosplenomegaly, and skeletal disease. Enzyme replacement therapy (ERT) has been proven to prevent progressive manifestations of Gaucher disease and effective in improving anemia, thrombocytopenia, bone markers and biomarkers. However, some patient needs still remain unmet because of the inaccessibility of certain sites including brain, bone and various organs. ERT could not Improve the irreversible lesion such as liver fibrosis, hepatopulmonary syndrome, and necrosis or infarction of bone and other organs. Adult patients with Gaucher disease should be screened for longterm complication such as bone disease, pulmonary hypertension, gallstone, and cancer, especially in patients with splenectomy. Parkinsonism and polyneuropathy was also reported among patients with type 1 Gaucher disease, but ERT does not improve neurological function. We need to review the benefits and unmet needs of ERT in Gaucher disease.

Smith-Lemli-Opitz syndrome (SLO) is a rare, autosomal recessive disease caused by an inborn error in cholesterol synthesis. Patients with this disease suffer from multiple malformations due to reduced activity of 7-dehydrocholesterol reductase (DHCR7), which increases 7-dehydrocholesterol (7DHC) and 8-dehydrocholesterol (8DHC) concentrations and decreases cholesterol concentration in body fluids and tissue. Here, we describe Korean siblings with SLO who were diagnosed recently, and performed a review of literature about Korean cases with SLO to date. Microcephaly and syndactyly of the second and third toes are the most common physical finding in SLOS patients. Other malformations including growth failure, cleft palate or bifid uvula, various heart malformation, genital ambiguity in males are also accompanied. Not all patients showed low levels of serum cholesterol, so DHCR7 mutation analysis can be helpful to confirmative diagnosis. Two mutations on p.R352 locus (p.R352W and p.R352Q) are commonly identified in Korean SLO patients. Although rare in Korea, SLO should be considered in the differential diagnosis of growth failure with intellectual disability, especially in patients with multiple congenital anomalies.

부신백질형성장애는 성염색체-연관성 유전대사 질환으로 ABCD1 유전자의 돌연변이에 의해 발생한다. 이중 대뇌 부신백질형성장애는 부신백질형성장애의 한 표현형으로, 급격한 뇌백질의 탈수초화와 부신 기능 부전을 보인다. 9세 남아가 인지 및 신경 기능의 퇴행을 주소로 내원하여 시행한 혈청 내 매우 긴 사슬 지방산이 증가되어 있었고 뇌 MRI에서 특징적인 양쪽 두정-후두엽 백질의 대칭적 고신호강도 소견을 보였으며 ABCD1 유전자에 돌연변이 c. 1252C>T (p.Arg418 Trp)가 발견되어 이를 보고하는 바이다.

스미스-렘리-오피츠 증후군은 상염색체 열성유전질환으로 콜레스테롤 합성의 장애로 나타나는 질병이다. 7-dehydrochlolesterol reductase 유전자의 변이로 인하여 콜레스테롤을 합성하지 못함으로써 정신지체, 자폐증, 발육부진, 내부장기 기형, 손과 발의 기형, 면역기능 저하, 소화기 및 시력의 문제 등이 나타난다. 이 질환은 경미한 증상에서부터 치명적인 증상까지 다양한 스펙트럼을 가진다. 저자들은 다양한 기형을 가진 환아에서 조기에 스미스-렘리-오피츠 증후군을 유전자 분석을 통하여 진단하였으며, 조기 진단 후 식이진행 및 기형에 대한 치료, 콜레스테롤을 보충 하였으며, 이를 문헌고찰과 함께 보고하는 바이다.

X-linked adrenoleukodystrophy (ALD) is a uncommon metabolic disorder which derived by peroxismal ${\beta}$-oxidation and elevation of serum very long chain fatty acid (VLCFA). VLCFA is mainly accumulated in the myelin of the central nervous system and adrenal cortex, by which the expressed symptoms of this disease are mainly neurologic and endocrinologic (such as adrenal insufficiency). The mutations in the ABCD1 gene causes X-linked ALD, nevertheless its phenotypes and genotypes are poorly coordinated. We report the case of a 12-year-old boy with X-linked ALD who developed vomiting, fatigue and poor oral intake. Severe dehydration and hyponatremia were found in initial physical examination and laboratory test, but his motor/sensory nerve function and mental status were completely normal. We diagnosed ALD with diffuse high-intensity signal in both parietotemporal cerebellar white matter in brain MRI and elevated serum VLCFA. Later, we confirmed a novel c.1635-1G>A (IVS6-1G>A) mutations of the ABCD1 gene. With the discrepancy between its phenotypes and genotypes, various phenotypes could be seen in X-ALD patient. Careful examination and further studies for these patients will be needed.