A novel DAX1 gene mutation in a Turkish infant with X-linked adrenal hypoplasia congenita

Adrenal hypoplasia congenita (AHC) is a rare inherited disorder of the adrenal cortex commonly manifested as an early onset adrenal insufficiency syndrome. A novel DAX1 (NR0B1) gene mutation was detected in a Turkish newborn boy presenting with primary adrenal insufficiency. He was from a family with a history of unexplained death of three male siblings in the neonatal period. This report highlights the value of mutational analysis of the DAX1 gene for definitive diagnosis of AHC as well as for genetic counselling because this disorder shows an X-linked genetic pattern of transmission, providing the possibility of finding new cases even in presymptomatic individuals.     

Presymptomatic diagnosis of X-linked adrenal hypoplasia congenita by analysis of DAX1

A novel DAX1 mutation (L381H) was discovered in the asymptomatic 8-month-old brother of a boy with primary adrenal failure. The infant had impaired adrenal reserve despite normal basal adrenal steroid concentrations. This case highlights the value of genetic testing in children at risk of the development of X-linked adrenal hypoplasia congenita before the onset of a potentially life-threatening adrenal crisis.     

Delayed diagnosis of adrenal hypoplasia congenita in a patient with a new mutation in the NR0B1 gene

Determining the precise cause of adrenal insufficiency occurring in infancy is of critical importance for both the correct management of affected children and the provision of correct genetic advice to their families. We report a case of a 24-year-old, male patient bearing a new mutation in the DAX1 gene. The patient was born at term, from a healthy pregnancy. Adrenal insufficiency was diagnosed in the fourth week of life with a salt-wasting syndrome, but it was mistakenly believed to be secondary to congenital adrenal hyperplasia (CAH). On hydrocortisone substitution, the child continued to develop normally, but the diagnosis of CAH was questioned, which led to an episode of an abrupt withdrawal of hydrocortisone substitution and subsequently caused a reoccurrence of a life-threatening salt-wasting syndrome. Owing to close follow-up, the patient's gonadal axis deficiency was promptly identified, which allowed an assisted but successful onset of puberty. We proposed the diagnosis of adrenal hypoplasia congenita (AHC) in this patient and identified a hemizygous mutation (c.1130delAinsGT, p.E377GfsX12) in exon 1 of the NR0B1 gene. To our knowledge, the detected mutation has not been described previously (HGMD Professional 2010.4, Human Gene Mutation Database, Biobase, Beverly, MA, USA). It leads to a frameshift, a premature stop codon, and, most likely, non-sense-mediated decay of the mutant mRNA. In this case, close patient follow-up minimized the detrimental consequences of an incorrect diagnosis. Nevertheless, it highlights the importance of the early precise diagnosis of patients with AHC.     

先天性肾上腺发育不良家系中DAX-1新突变的发现

目的探讨1个先天性肾上腺发育不良家系的临床特征,检测患者及其家属中是否存在剂量敏感的性别反转．先天性肾上腺发育不良基因1（DAX-1）突变。方法对1个家系的两例患者相关医学检查获取临床资料,并取得含患者在内的20名家系成员的外周血液标本;PCR扩增DAX-1的全部外显子。扩增产物经纯化后直接测序进行基因检测。结果2例患者DAX-1第一外显子处均存在T785C半合子突变,家系中有5例女性为此突变的携带者。结论在1个中国人先天性肾上腺发育不良家系中发现DAX-1新的点突变T785C。     

Extreme hyponatremia in an infant with congenital adrenal hypoplasia due to a novel NR0B1 (DAX-1) mutation

BACKGROUND: Extreme hyponatremia (<105 mmol/l) has rarely been reported in infants. It is potentially life-threatening and requires intensive care treatment. PATIENT: We report on a male infant with absence of weight gain from birth to day 33 of life despite adequate nutrition. On admission serum sodium and potassium were 104 and 5.9 mmol/L respectively. The infant's physical status revealed dehydration, but normal activity with no apparent neurological, circulatory or respiratory impairment. MAIN RESULTS: Global adrenocortical insufficiency was diagnosed and treated with hormonal substitution in addition to intravenous application of fluid, glucose and electrolytes. The rise of serum sodium was carefully monitored and adjusted to a target rate of 0.5 mmol/L/h. X-linked adrenal hypoplasia congenita (X-AHC) was confirmed by the identification of a novel nonsense NR0B1 (DAX-1) mutation (W236X). CONCLUSIONS: X-AHC in infants may present as failure to thrive despite adequate nutrition. Extreme hyponatremia may be associated with little symptoms if developing slowly. Rehydration and slow correction of serum sodium with solutions containing less sodium than normal saline is essential.     

An atypical kindred with X-linked adrenal hypoplasia congenita, normal puberty, and normal Dax-1 promoter and coding sequence

We report a Chinese kindred with an atypical sex-linked form of isolated adrenal hypoplasia without hypogonadotropic hypogonadism. Evidence of sex linkage was supported by DNA analysis using three polymorphic markers from the X-chromosome: a restriction fragment length polymorphism 200 kb centromeric of the DAX-1 gene, a tetranucleotide repeat marker in the DAX-1 promoter (DAX-P), and a microsatellite in the Duchenne muscular dystrophy locus (3'-19). This pedigree therefore presents the novel phenotype of sex-linked hypoadrenalism without hypogonadotropic hypogonadism, with evidence of possible linkage to the DAX-1 gene. However, all three affected individuals were examined for mutations in the DAX-1 gene, and found to have no sequence anomalies in the coding region, splice sites or 5' non-coding region. This presentation may be due to a defect in the DAX-1 gene outside its known coding region, possibly modulated by functional polymorphisms at other loci, and/or environmental effects, or to a defect in a novel gene on the X chromosome which selectively influences adrenal development.     

X-linked adrenal hypoplasia congenita: a novel <Emphasis Type="Italic">DAX1</Emphasis> missense mutation and challenges for clinical diagnosis in Africa

Adrenal hypoplasia congenita (AHC) is a rare disease. The X-linked form of AHC is caused by deletions or mutations in DAX1 gene and has a variable clinical presentation. To date, no data on X-linked AHC in central Africa are available. Here, we report a Congolese pedigree with several cases of unexplained deaths of male infants. A careful analysis of the pedigree of this family lead to the recognition of an X-linked inheritance pattern, with subsequent confirmation in a female heterozygous carrier of a DAX1 missense mutation c.1274G>T, (p.Arg425Ile).The diagnosis of this condition remains challenging in a developing country, since the manifestations of AHC overlap with those of the much more frequently occurring infections; darkening of the skin is difficult to evaluate and there is a lack of access to routine endocrinological testing. The diagnosis was eventually made based on the family pedigree, evoking an X-linked inheritance pattern. This illustrates the necessity for medical and clinical genetics to be part of the curriculum of medical school in developing countries.     

先天性肌强直两家系的临床分析及CLCN1基因突变检测

目的研究先天性肌强直(MC)两家系的临床特点及CLCN1基因突变情况。方法对两个MC家系7例患者的临床资料进行分析。从两个家系成员及100例正常对照者外周静脉血中提取基因组DNA,通过PCR及DNA测序对CLCN1编码区进行突变分析。结果两个家系的7例患者均为幼年起病的肌强直与运动笨拙,伴有肌肥大和扣击性肌球,肌电图示肌强直电位发放。基因检测发现先证者1及家系1其他患者在第8外显子892位核苷酸处发生G-A杂合突变,使298位丙氨酸被苏氨酸代替(A298T)。而另一家系患者及其他健康成员CLCN1基因23对外显子直接测序均未发现有突变存在。结论在中国MC家系中发现了新的CLCN1突变位点,为研究中国人群CLCN1突变类型、遗传方式提供了一定的参考。     

Mutation screening of the BTK gene in 56 families with X-linked agammaglobulinemia (XLA): 47 unique mutations without correlation to clinical course

OBJECTIVES: To determine the utility of single-stranded conformation polymorphism (SSCP) analysis for mutation screening in the BTK (Bruton's tyrosine kinase) gene, we investigated 56 X-linked agammaglobulinemia (XLA) families. To obtain genotype/ phenotype correlations, predicted protein aberrations were correlated with the clinical course of the disease. PATIENTS: This study included 56 patients with XLA, with or without a positive family history, who were diagnosed on the basis of their clinical features, low peripheral B-cell count, and low immunoglobulin levels. Ten patients with isolated hypogammaglobulinemia and 50 healthy males served as controls. METHODS: SSCP analysis was performed for the entire BTK gene, including the exon-intron boundaries and the promoter region. Structural implications of the missense mutations were investigated by molecular modeling, and the functional consequences of some mutations also were evaluated by in vitro kinase assays and Western blot analysis. RESULTS: We report the largest series of patients with XLA to date. All but 5 of the 56 index patients with XLA screened with SSCP analysis showed BTK gene abnormalities, and in 2 of the 5 SSCP-negative patients, no BTK protein was found by Western blot analysis. There were 51 mutations, including 37 novel ones, distributed across the entire gene. This report contains the first promoter mutation as well as 14 novel missense mutations with the first ones described for the Tec homology domain and the glycine-rich motif in the SH1 domain. Each index patient had a different mutation, except for four mutations, each in two unrelated individuals. This result supports the strong tendency for private mutations in this disease. No mutations were found in the controls. CONCLUSIONS: Our results demonstrate that molecular genetic testing by SSCP analysis provides an accurate tool for the definitive diagnosis of XLA and the discrimination of borderline cases, such as certain hypogammaglobulinemia or common variable immunodeficiency patients with overlapping clinical features. Genotype/ phenotype correlations are not currently possible, making prediction of the clinical course based on molecular genetic data infeasible.     

A novel missense mutation in the DKC1 gene in a Japanese family with X-linked dyskeratosis congenita

The authors report 2 male patients with dyskeratosis congenita (DC) in a Japanese kindred. Sequencing of the complementary DNA of the dyskerin gene (DKC1) revealed a T-to-C transition at nucleotide 1285 in exon 12 that resulted in a novel missense mutation L398P. Despite harboring the same mutation in the DKC1 gene, one patient had significantly milder hematological symptoms than the other, indicating that there may be other factors that determine the severity of DC.     

2例X-连锁低血磷性佝偻病患者PHEX基因新发突变的研究

目的研究2例X-连锁低血磷性佝偻病(XLH)患儿及家系磷酸盐调节基因(PHEX)的突变类型,以明确其遗传学病因。方法回顾性分析2例XLH患者临床资料,应用高通量测序技术从基因组水平对先证者的XLH致病基因PHEX进行检测,并应用PCR-Sanger测序法对突变基因的家系分布进行验证。结果 2例患儿均检测到PHEX基因新发突变,1例为移码突变c.931dupC,导致翻译提前终止,产生截短蛋白p.Gln311Profs*13;另1例为剪接位点突变IVS14+1GA,导致外显子15跳跃,产生不完整的氨基酸链。2例患儿父母的基因表型均正常。结论 c.931dup C和IVS14+1GA是PHEX基因的两个新突变,可能是XLH新的致病性突变。     

Further delineation of the congenital form of X-linked dyskeratosis congenita (Hoyeraal-Hreidarsson syndrome)

Hoyeraal-Hreidarsson syndrome represents a severe variant of dyskeratosis congenita (Zinsser-Cole-Engman syndrome). This X-linked recessive, progressive, multisystemic disorder reported so far in 12 pedigrees is characterised by intrauterine growth retardation, microcephaly, cerebellar hypoplasia, mental retardation, progressive combined immune deficiency and aplastic anaemia. Mutations in the DKC1gene on Xq28 have been identified in the X-linked form of dyskeratosis congenita and in some Hoyeraal-Hreidarsson syndrome patients. We report on two sibs and two other unrelated patients with the striking clinical features of Hoyeraal-Hreidarsson syndrome. Noticeably, all four had early digestive problems, with chronic, bloody diarrhoea and feeding problems causing one of the most difficult problems in the supportive treatment of this uniformly lethal condition. Pathological changes in the proliferative compartment of the digestive mucosa included alterations of the glandular architecture and focal rarefaction of the glands. This aspect seems consistent with altered telomerase function associated with a dyskerin mutation which may decrease the proliferative capacity of digestive epithelial cells. A missense mutation 146 CT (Thr49Met) in the DKC1gene was found in two unrelated patients, whereas mutation screening was negative for one single case. The absence of mutations of the DKC1gene in patients with Hoyeraal-Hreidarsson syndrome emphasises the probable implication of one or more other loci.Abbreviations DC dyskeratosis congenita syndrome - HH Hoyeraal-Hreidarsson syndrome - IUGR intrauterine growth retardation     

Three missense mutations in the galactose-1-phosphate uridyltransferase gene of three families with mild galactosaemia

Classical galactosaemia caused by deficiency of galactose-1-phosphate uridyltransferase (GALT) is characterized by acute symptoms of hepatocellular dysfunction, sepsis, cataracts and failure to thrive. Galactose limitation reverses these complications immediately, however, most of these children have a long-term complication of verbal dyspraxia, mental retardation and ovarian failure. The GALT gene was cloned and several mutations including the common Q188R have been reported. In this study the coding region of GALT was amplified by polymerase chain reaction from genomic DNA of classical galactosaemic individuals and characterized by direct sequencing of the products. Three missense mutations were identified in three patients with a mild galactosaemic variant: (1) replacement of threonine-138 by methionine (T138M); (2) replacement of arginine by tryptophan (R259W); and (3) replacement of threonine by alanine (T350A). All three galactosaemic individuals, one girl and two boys, have varying degrees of residual GALT activity in RBC and their galactose-1-phosphate levels decreased much faster than in other galactosaemic patients. These misense mutations occur in regions that are not highly conserved domains.Conclusion The study of the molecular basis related to the phenotype variation may indeed help to prognosticate the outcome of patients with classical galactosaemia.