Hirotake Sawada

Cytochrome P450 oxidoreductase deficiency: identification and characterization of biallelic mutations and genotype-phenotype correlations in 35 Japanese patients.

CONTEXT Cytochrome P450 oxidoreductase (POR) deficiency is a rare autosomal recessive disorder characterized by skeletal dysplasia, adrenal dysfunction, disorders of sex development (DSD), and maternal virilization during pregnancy. Although multiple studies have been performed for this condition, several matters remain to be clarified, including the presence of manifesting heterozygosity and the underlying factors for clinical variability. OBJECTIVE The objective of the study was to examine such unresolved matters by detailed molecular studies and genotype-phenotype correlations. PATIENTS Thirty-five Japanese patients with POR deficiency participated in the study. RESULTS Mutation analysis revealed homozygosity for R457H in cases 1-14 (group A), compound heterozygosity for R457H and one apparently null mutation in cases 15-28 (group B), and other combinations of mutations in cases 29-35 (group C). In particular, FISH and RT-PCR sequencing analyses revealed an intragenic microdeletion in one apparent R457H homozygote, transcription failure of apparently normal alleles in three R457H heterozygotes, and nonsense mediated mRNA decay in two frameshift mutation-positive cases examined. Genotype-phenotype correlations indicated that skeletal features were definitely more severe, and adrenal dysfunction, 46,XY DSD, and pubertal failure were somewhat more severe in group B than group A, whereas 46,XX DSD and maternal virilization during pregnancy were similar between two groups. Notable findings also included the contrast between infrequent occurrence of 46,XY DSD and invariable occurrence of 46,XX DSD and pubertal growth pattern in group A mimicking that of aromatase deficiency. CONCLUSIONS The results argue against the heterozygote manifestation and suggest that the residual POR activity reflected by the R457H dosage constitutes the underlying factor for clinical variability in some features but not other features, probably due to the simplicity and complexity of POR-dependent metabolic pathways relevant to each phenotype.

Infantile Cases of Sitosterolaemia with Novel Mutations in the ABCG5 Gene: Extreme Hypercholesterolaemia is Exacerbated by Breastfeeding.

Few data exists regarding the clinical impact of breastfeeding in infantile sitosterolaemic cases. We report four Japanese infantile cases of sitosterolaemia, an extremely rare inherited disease characterised by increased serum levels of plant sitosterol, presenting with severe hypercholesterolaemia and systemic xanthomas exacerbated by breastfeeding. In these four cases, genetic analyses were performed for low-density lipoprotein (LDL) receptor, proprotein convertase subtilisin/kexin type 9 (PCSK9), LDL receptor adaptor protein 1 and ATP-binding cassette (ABC) subfamily G member 5 and 8 (ABCG5 and ABCG8) genes. We assessed their clinical manifestations, including responsiveness to a variety of treatments, especially to weaning from breastfeeding and use of ezetimibe. Two pairs of mutations in the ABCG5 gene in each case, including two novel mutations (c.130C>T or p.Ser44Ala and c.1813_1817delCTTTT or p.Pro558GlufsX14) and two known mutations (c.1306G>A or p.Arg389His and c.1336C>T or p.Arg446X), were identified. Significant reductions in cholesterol levels were obtained by means of weaning from breastfeeding alone. Substantial reductions in sitosterol levels, without any apparent side effects, were observed with ezetimibe. In conclusion, we have identified infantile Japanese sitosterolaemic subjects with extreme hypercholesterolaemia exacerbated by breastfeeding. Their unique response to weaning from breastfeeding, as well as to use of ezetimibe, could provide insights into the metabolic basis of sterols in humans.

A novel mutation of the PHKA2 gene in a patient with X-linked liver glycogenosis type 1

XLG is classified into two types: XLG1 and XLG2. Although the clinical findings are very similar and Phk activity is not detected in liver biopsy specimens for either type, the Phk activity in blood cells is decreased in XLG1, but is normal or even enhanced in XLG2. From previous studies, XLG1 seems to be caused by nonsense mutations or a large deletion, whereas XLG2 is usually caused by missense mutations, of the PHKA2 gene (Fig. 1). In this paper, we report an interesting case of XLG1 caused by a missense mutation of the PHKA2 gene.

Molecular and clinical features of KATP -channel neonatal diabetes mellitus in Japan.

There are few reports pertaining to Asian patients with neonatal diabetes mellitus (NDM) caused by activating mutations in the ATP‐sensitive potassium channel genes (KATP‐NDM).

Incidence and Characteristics of Adrenal Crisis in Children Younger than 7 Years with 21-Hydroxylase Deficiency: A Nationwide Survey in Japan

Background/Aims: We aimed to evaluate the incidence and characteristics of adrenal crisis in Japanese children with 21-hydroxylase deficiency (21-OHD). Methods: We conducted a retrospective nationwide survey for the councilors of the Japanese Society for Pediatric Endocrinology (JSPE) regarding adrenal crisis in children under 7 years with 21-OHD, admitted to hospitals from 2011 through 2016. We defined adrenal crisis as the acute impairment of general health due to glucocorticoid deficiency with at least two of symptoms, signs, or biochemical abnormalities. Results: The councilors of the JSPE in 83 institutions responded to this survey (response rate, 60.1%). Data analyses of 378 patients with 1,101.4 person-years (PYs) revealed that 67 patients (17.7%) experienced at least 1 episode of hospital admission for adrenal crisis at the median age of 2 years. The incidence of adrenal crisis was calculated as 10.9 per 100 PYs (95% confidence interval [CI] 9.6–12.2). Infections were the most common precipitating factors, while no factor was observed in 12.5%. Hypoglycemia occurred concomitantly in 27.4%. One patient died from severe hypoglycemia, resulting in a mortality rate of 0.09 per 100 PYs (95% CI 0.0–0.2). Conclusion: Adrenal crisis is not rare and can be accompanied by disastrous hypoglycemia in children with 21-OHD.

Development of a novel ultrasensitive enzyme immunoassay for human glutamic acid decarboxylase 65 antibody

Background We developed a novel, ultrasensitive enzyme immunoassay (immune complex transfer enzyme immunoassay) for determination of glutamic acid decarboxylase autoantibody concentrations in serum samples from patients with type 2 diabetes. Methods We developed an immune complex transfer enzyme immunoassay for glutamic acid decarboxylase autoantibody and measured glutamic acid decarboxylase autoantibody from 22 patients with type 1 diabetes, 29 patients with type 2 diabetes, and 32 healthy controls. Results A conventional ELISA kit identified 10 patients with type 1 diabetes and one patient with type 2 diabetes as glutamic acid decarboxylase autoantibody positive, whereas 15 patients with type 1 diabetes and six patients with type 2 diabetes were identified as glutamic acid decarboxylase autoantibody positive using immune complex transfer enzyme immunoassay. Conclusions Immune complex transfer enzyme immunoassay is a highly sensitive and specific assay for glutamic acid decarboxylase autoantibody and might be clinically useful for diabetic onset prediction and early diagnosis.

Nephrotic syndrome complicated by idiopathic central diabetes insipidus

BackgroundThere is ongoing discussion regarding the mechanisms underlying edema formation in nephrotic syndrome (NS). Many studies published in the last decade reported that primary renal sodium retention was a major factor in edema formation. However, many of the factors influencing edema formation in NS remain unclear, including the role of arginine vasopressin (AVP).Case-Diagnosis/TreatmentWe report a 12-year-old boy with steroid-dependent NS complicated by idiopathic central diabetes insipidus (CDI). He did not develop edema during his first relapse of NS after developing CDI, despite having hypoalbuminemia. He had polydipsia, polyuria, low urine osmolality, and a low serum arginine AVP level. His fractional excretion of sodium was only slightly low. Endocrinological testing and magnetic resonance imaging revealed idiopathic CDI. After starting desmopressin therapy, he developed edema when his NS relapsed.ConclusionsThis is the first known reported case of NS in a patient with CDI. The findings suggest that appropriate AVP secretion in response to an increase in serum osmolality caused by renal sodium retention is necessary for excess extracellular fluid accumulation in NS. Further investigation is needed to more fully understand the role of AVP in edema formation in NS.

A hot-spot mutation in CDC42 (p.Tyr64Cys) and novel phenotypes in the third patient with Takenouchi-Kosaki syndrome

Takenouchi-Kosaki syndrome (TKS) is a congenital malformation syndrome characterized by severe developmental delay, macrothrombocytopenia, camptodactyly, sensorineural hearing loss, and dysmorphic facial features. Recently, a heterozygous de novo mutation (p.Tyr64Cys) in the CDC42 gene, which encodes a key small GTP-binding protein of the Rho-subfamily, was identified in two unrelated patients with TKS. We herein report a third patient with TKS who had the same heterozygous CDC42 mutation. The phenotype of the patient was very similar to those of the two previously reported patients with TKS; however, she also demonstrated novel clinical manifestations, such as congenital hypothyroidism and immunological disturbance. Thus, despite the heterozygous mutation of CDC42 (p.Tyr64Cys) likely being a hot-spot mutation for TKS, its phenotype may be variable. Further studies and the accumulation of patients with CDC42 mutations are needed to clarify the phenotype in patients with TKS and the pathophysiological roles of the CDC42 mutation.

TRPV6 Variants Interfere with Maternal-Fetal Calcium Transport through the Placenta and Cause Transient Neonatal Hyperparathyroidism

Transient neonatal hyperparathyroidism (TNHP) is etiologically a heterogeneous condition. One of the etiologies is an insufficient maternal-fetal calcium transport through the placenta. We report six subjects with homozygous and/or compound-heterozygous mutations in the gene encoding the transient receptor potential cation channel, subfamily V, member 6 (TRPV6), an epithelial Ca2+-selective channel associated with this condition. Exome sequencing on two neonates with skeletal findings consistent with neonatal hyperparathyroidism identified homozygous frameshift mutations before the first transmembrane domain in a subject born to first-cousins parents of Pakistani descent as well as compound-heterozygous mutations (a combination of a frameshift mutation and an intronic mutation that alters mRNA splicing) in an individual born to a non-consanguineous couple of African descent. Subsequently, targeted mutation analysis of TRPV6 performed on four other individuals (born to non-consanguineous Japanese parents) with similar X-rays findings identified compound-heterozygous mutations. The skeletal findings improved or resolved in most subjects during the first few months of life. We identified three missense variants (at the outer edges of the second and third transmembrane domains) that alter the localization of the TRPV6: one recurrent variant at the S2-S3 loop and two recurrent variants (in the fourth ankyrin repeat domain) that impair TRPV6 stability. Compound heterozygous loss-of-function mutations for the pathogenic frameshift allele and the allele with an intronic c.607+5G>A mutation resulted in the most severe phenotype. These results suggest that TNHP is an autosomal-recessive disease caused by TRPV6 mutations that affect maternal-fetal calcium transport.

Osteogenesis imperfecta complicated with renal hypoplasia leads to chronic kidney disease

An 8-year-old boy with type III osteogenesis imperfecta (OI) was referred for the management of frequent bone fractures. His height and weight were 75.0 cm and 8.0 kg, respectively, and he presented with severe deformity. The patient was born by cesarean section, with a birthweight of 1980 g at a gestational age of 38 weeks, owing to intrauterine growth retardation (IUGR). He was subsequently diagnosed with OI because of fragile bones with frequent fractures. He did not have any history of acute kidney injury or use of nephrotoxic drugs during the neonatal period. Cyclic i.v. pamidronate was initiated at 11 years of age. It was administered at a dose of 1 mg/kg on 3 successive days, and the infusion cycle was repeated every 4 months. Laboratory examination before the commencement of the first treatment indicated proteinuria (1+), but serum creatinine was within the normal range at 0.1 mg/dL. I.v. pamidronate reduced the bone pain and fracture rate. Proteinuria persisted after the treatment, but it did not increase. Five years after treatment initiation, massive proteinuria and renal dysfunction became apparent at the age of 16 years. At that time, height and weight were 91.0 cm and 16.1 kg, respectively. Laboratory findings were as follows: urinary protein/creatinine ratio, 3.16 g/g creatinine; serum albumin, 3.41 g/dL; serum creatinine, 0.61 mg/dL; and creatinine-based estimated glomerular filtration rate (eGFR), 50.1 mL/min/ 1.73 m. Hematuria and peripheral edema were not seen, and nephrotic syndrome did not develop. On ultrasonography the right and left kidneys were 6.2 and 5.9 cm in length, respectively, with high echogenicity (Fig. 1a,b). Technetium-99m dimercaptosuccinic acid (Tc DMSA) scintigraphy showed reduced radionuclide uptake in both kidneys (Fig. 1c). Vesicoureteric reflux was not detected. Kidney biopsy indicated low glomerular density and enlarged glomeruli (Fig. 1d–f). On electron microscopy there was mild thickening of the glomerular basement membranes without podocyte foot process effacement. Based on these findings, a final diagnosis of renal hypoplasia caused by oligomeganephronia was made. Subsequently, the i.v. pamidronate was discontinued and treatment initiated treatment with valsartan, an angiotensin II receptor blocker. By the age of 19 years, renal function had deteriorated despite treatment with valsartan; serum creatinine and creatinine-based eGFR were 1.27 mg/dL and 25.6 mL/ min/1.73 m, respectively.