Ja Hye Kim

Pathophysiology and clinical characteristics of hypothalamic obesity in children and adolescents

The hypothalamus plays a key role in the regulation of body weight by balancing the intake of food, energy expenditure, and body fat stores, as evidenced by the fact that most monogenic syndromes of morbid obesity result from mutations in genes expressed in the hypothalamus. Hypothalamic obesity is a result of impairment in the hypothalamic regulatory centers of body weight and energy expenditure, and is caused by structural damage to the hypothalamus, radiotherapy, Prader-Willi syndrome, and mutations in the LEP, LEPR, POMC, MC4R and CART genes. The pathophysiology includes loss of sensitivity to afferent peripheral humoral signals, such as leptin, dysregulated insulin secretion, and impaired activity of the sympathetic nervous system. Dysregulation of 11β-hydroxysteroid dehydrogenase 1 activity and melatonin may also have a role in the development of hypothalamic obesity. Intervention of this complex entity requires simultaneous targeting of several mechanisms that are deranged in patients with hypothalamic obesity. Despite a great deal of theoretical understanding, effective treatment for hypothalamic obesity has not yet been developed. Therefore, understanding the mechanisms that control food intake and energy homeostasis and pathophysiology of hypothalamic obesity can be the cornerstone of the development of new treatments options. Early identification of patients at-risk can relieve the severity of weight gain by the provision of dietary and behavioral modification, and antiobesity medication. This review summarizes recent advances of the pathophysiology, endocrine characteristics, and treatment strategies of hypothalamic obesity.

Clinical, endocrinological, and molecular characterization of Kallmann syndrome and normosmic idiopathic hypogonadotropic hypogonadism: a single center experience

Purpose Isolated gonadotropin-releasing hormone (GnRH) deficiency (IGD) is classified as Kallmann syndrome (KS) with anosmia and normosmic idiopathic hypogonadotropic hypogonadism (nIHH). This study was undertaken to investigate the clinical, endocrinological, and molecular characteristics in Korean patients with KS and nIHH. Methods Twenty-six patients from 25 unrelated families were included. Their clinical, endocrinological, and radiological findings were analyzed retrospectively. Mutation analysis of the GNRH1, GNRHR, KISS1, KISS1R, PROK2, PROKR2, TAC3, TACR3, FGF8, FGFR1, and KAL1 genes was performed in all patients. CHD7 and SOX10 were analyzed in patients with CHARGE (Coloboma, Heart defects, choanae Atresia, Growth retardation, Genitourinary abnormality, Ear abnormality) features or deafness. Results Of the 26 patients, 16 had KS and 10 had nIHH. At diagnosis, mean chronologic age was 18.1 years in males and 18.0 years in females; height SDS were -0.67±1.35 in males, -1.12±1.86 in females; testis volume was 2.0±1.3 mL; and Tanner stage was 1.5. There were associated anomalies in some of the KS patients: hearing loss (n=6) and congenital heart disease (n=4). Absence or hypoplasia of the olfactory bulb/sulci was found in 84.62% of patients with KS. Molecular defects in KAL1, SOX10, and CHD7 were identified in 5 patients from 4 families (16.0%, 4/25 pedigrees). After sex hormone replacement therapy, there were improvement in sexual characteristics and the sexual function. Conclusion This study described the clinical, endocrinological, and molecular genetic features in IGD patients in Korea. Although the mutation screening was performed in 10 genes that cause IGD, molecular defects were identified in relatively small proportions of the cohort.

Long-term enzyme replacement therapy for Fabry disease: efficacy and unmet needs in cardiac and renal outcomes

Fabry disease is a progressive lysosomal storage disease caused by alpha-galactosidase A deficiency. This condition is characterized by progressive accumulation of glycosphingolipids with functional impairment in various organs, including the kidney, heart and cerebrovascular system. Enzyme replacement therapy (ERT) is essential because it attenuates the disease progression. The present study investigated the long-term efficacy of ERT in 19 Korean Fabry patients (11 adult males, 4 symptomatic female carriers and 4 pediatric males) who had received ERT for 8.1±2.2 years (range, 5.3–10.5 years). In the 11 adult males, the mean reduction in the estimated glomerular filtration rate (eGFR) was −3.8±4.5 ml−1 min 1.73 m–2. The rate of eGFR decline was significantly lower in patients with lower proteinuria (<1 g per day) before ERT. The left ventricular mass index decreased or was stable throughout the ERT in male patients with or without left ventricular hypertrophy before ERT initiation. In female carriers and pediatric male patients, renal and cardiac functions remained stable with ERT. Arrhythmias were observed in 10 adult males and 1 female patient before ERT and persisted during ERT. One pediatric patient newly developed arrhythmia despite ERT. In conclusion, long-term ERT has beneficial effects on the renal and cardiac outcomes of Fabry patients but has limited effect in patients with irreversible organ damage. Identification of patients in the early disease stage and rapid ERT initiation might be the best strategy to improve the natural course of the disease.

Lowe syndrome: a single center's experience in Korea

Purpose Lowe syndrome is a rare, X-linked recessive disorder caused by mutations in the OCRL gene. It involves multiple anatomic systems, particularly the eyes, central nervous system, and kidneys, and leads to profound growth failure and global developmental delay. This study evaluated the clinical and genetic characteristics of Korean patients with Lowe syndrome. Methods The clinical findings and results of genetic studies were reviewed for 12 male patients diagnosed with Lowe syndrome at a single medical institution. Results The mean age of the patients at presentation was 2.2 months (range, 0-4 months), although the diagnosis was delayed by a mean of 2.8 years (range, 0-9.7 years). The mean follow-up period was 9.0 years (range, 0.6-16.7 years). Nine mutations in OCRL were identified in 11 patients (92%), with three novel mutations. The main presentation was congenital cataract in both eyes necessitating early cataract removal in the 11 patients with impaired visual acuity. Profound short stature and developmental delay were observed in all patients, and seizures occurred in 50% of the patients. All patients suffered from proximal renal tubular dysfunction, and one patient developed chronic renal failure. Other manifestations included pathologic fracture (50%), cutaneous cysts (42%), and cryptorchidism (42%). However, there was no bleeding tendency, and none of the patients died during the study period. Conclusion This study describes the clinical and genetic characteristics of Korean patients with Lowe syndrome. The observations are helpful for understanding the natural courses of Lowe syndrome and for appropriate genetic counseling.

Clinical outcomes and the mutation spectrum of the OTC gene in patients with ornithine transcarbamylase deficiency

Ornithine transcarbamylase (OTC) deficiency is an X-linked inborn error of the urea cycle that leads to the accumulation of ammonia, resulting in neurological deficits. This study was performed to describe the clinical outcomes, biochemical features and molecular spectra of patients with OTC deficiency. A total of 49 patients from 47 unrelated Korean pedigrees were included who were diagnosed with OTC deficiency based on biochemical findings and molecular analyses. Patient clinical features, biochemical findings and molecular data were analyzed retrospectively. Males with neonatal-onset phenotype presented with seizure or altered mentality (n=20). Biochemical findings showed high blood ammonia (1132.5±851.6 μmol l−1) and urine orotic acid (1840.7±1731.3 mmol mol−1 Cr) levels. There were also five males with late-onset disease who presented with vomiting, irritability and seizure at age 8.2±9.4 years old (range, 0.6–20 years). Symptomatic females presented with vomiting, seizure, and altered mentality at age 3.5±3.5 years (range, 0.2–12.8 years; n=24). More males with the late-onset form and symptomatic females displayed mild hyperammonemia and orotic aciduria compared with those showing a neonatal phenotype (P<0.05). Molecular analysis identified 37 different mutations (22 missense, 5 large deletions, 4 small deletions, 1 insertion, 3 nonsense and 2 splice sites) from all 49 patients; the mutations were dispersed throughout all coding exons. In Korean patients with OTC deficiency, mutations in OTC are genetically heterogeneous. Male patients with the neonatal-onset phenotype showed poor outcomes because of severe hyperammonemia. Early diagnosis and interventions for hyperammonemia can provide more favorable prognosis.

Allele frequency of a 24 bp duplication in exon 10 of the CHIT1 gene in the general Korean population and in Korean patients with Gaucher disease.

Plasma chitotriosidase activity is used for diagnosis and monitoring of Gaucher disease. However, homozygous duplication of a 24 bp region in exon 10 of the chitotriosidase gene (CHIT1) abolishes enzyme activity, limiting its use as a biomarker in Gaucher disease. This study investigates the allele frequency of the 24 bp duplication, in both the general Korean population and in patients with Gaucher disease. Fifteen Korean patients with Gaucher disease and 231 Korean normal individuals were enrolled. Genotyping was performed to identify the 24 bp duplication in exon 10 of CHIT1 using DNA extracted from peripheral leukocytes or dried blood spots. Two patients with Gaucher disease (13.3%) had normal plasma chitotriosidase activity, and carried a homozygous 24 bp duplication of exon 10 of the CHIT1 gene. Nine patients were heterozygote carriers (60.0%). Of the normal 231 Korean individuals, heterozygous duplication was detected in 109 individuals (47.2%) and homozygous duplication in 75 (32.5%). The allele frequency was 56.1% (95% confidence interval, 49.4–62.7%). The frequency of the 24 bp duplication was remarkably high in both Korean patients with Gaucher disease and in the normal population, limiting the efficacy of chitotriosidase as a biomarker in Gaucher disease in Korea. New biomarkers are required that consider the genetic characteristics of different populations.

Clinical, Biochemical, and Genetic Characterization of Glycogen Storage Type IX in a Child with Asymptomatic Hepatomegaly

Glycogen storage disease type IX (GSD IX) is caused by a defect in phosphorylase b kinase (PhK) that results from mutations in the PHKA2, PHKB, and PHKG2 genes. Patients usually manifest recurrent ketotic hypoglycemia with growth delay, but some may present simple hepatomegaly. Although GSD IX is one of the most common causes of GSDs, its biochemical and genetic diagnosis has been problematic due to its rarity, phenotypic overlap with other types of GSDs, and genetic heterogeneities. In our report, a 22-month-old boy with GSD IX is described. No other manifestations were evident except for hepatomegaly. His growth and development also have been proceeding normally. Diagnosed was made by histologic examination, an enzyme assay, and genetic testing with known c.3210_3212del (p.Arg1070del) mutation in PHKA2 gene.

Short-term efficacy of N-carbamylglutamate in a patient with N-acetylglutamate synthase deficiency

N-acetylglutamate synthase (NAGS) deficiency is a rare inborn error regarding the urea cycle, however, its diagnosis is important as it can be effectively treated by N-carbamylglutamate. We evaluated a patient with NAGS deficiency who harbored two novel NAGS mutations and who showed excellent responsiveness during 1 year of N-carbamylglutamate treatment.

Determination of Autosomal Dominant or Recessive Methionine Adenosyltransferase I/III Deficiencies Based on Clinical and Molecular Studies.

Methionine adenosyltransferase (MAT) I/III deficiency can be Inherited as autosomal dominant (AD) or as recessive (AR) traits in which mono- or biallelic MAT1A mutations have been identified, respectively. Although most patients have benign clinical outcomes, some with the AR form have neurological deficits. Here we describe 16 Korean patients with MAT I/III deficiency from 15 unrelated families identified by newborn screening. Ten probands had the AD MAT I/III deficiency, while six had AR MAT I/III deficiency. Plasma methionine (145.7 µmol/L versus 733.2 µmol/L, P < 0.05) and homocysteine levels (12.3 µmol/L versus 18.6 µmol/L, P < 0.05) were lower in the AD type than in AR type. In addition to the only reported AD MAT1A mutation, p.Arg264His, we identified two novel AD mutations, p.Arg249Gln and p.Gly280Arg. In the AR type, four previously reported and two novel mutations, p.Arg163Trp and p.Tyr335*, were identified. No exonic deletions were found by quantitative genomic polymerase chain reaction (PCR). Three-dimensional structural prediction programs indicated that the AD-type mutations were located on the dimer interface or in the substrate binding site, hindering MAT I/III dimerization or substrate binding, respectively, whereas the AR mutations were distant from the interface or substrate binding site. These results indicate that the AD or AR MAT I/III deficiency is correlated with clinical findings, substrate levels and structural features of the mutant proteins, which is important for the neurological management and genetic counseling of the patients.

Diverse genetic aetiologies and clinical outcomes of paediatric hypoparathyroidism

Hypoparathyroidism is characterized by hypocalcaemia, hyperphosphataemia, and low or inappropriately normal parathyroid hormone (PTH) levels. Idiopathic or genetic drivers are the predominant causes of hypoparathyroidism in paediatric‐age patients.