Determination of thyroid volume in infants with suspected congenital hypothyroidism-the limitations of both subjective and objective evaluation.

OBJECTIVE: To compare two methods of assessing gland size on thyroid ultrasound in newborn infants with suspected congenital hypothyroidism (CH). METHODS: Images from infants with eutopic glands referred between 2007 and 2013 were evaluated blind by two sets of observers. Subjective gland size was categorised as small, borderline-small, normal, borderline-large and large. Objective gland volume, calculated as the sum of each lobe using the prolate ellipsoid formula (length x width x depth x π/6), was put into corresponding categories: <0.8, 0.81-1.0, 1.1- <2.2, 2.2-2.4 and >2.4 ml, derived from normative Scottish data. RESULTS: Of 36 infants, permanent CH was present in 17, transient CH in 17, status uncertain in 2. Mean (SD) intraobserver error for thyroid volume measurement was 0.11 (0.23) ml [8.3%]. Subjective assessment by two observers was discordant in only four (10.8%) infants. However, subjective vs objective evaluation was discordant in 14 (39%). Eight (three permanent, five transient CH) had large glands subjectively but normal glands objectively; and six (four transient CH) had normal glands subjectively but small glands objectively. The former infants all showed a single flattened curve to the anterior thyroid margin, giving an impression of bulkiness. Gland shape was normal in the latter infants. CONCLUSION: Neither subjective nor objective evaluation predicts permanent vs transient CH. Altered gland shape may confound both methods, and undermine use of the conventional formula for measuring lobe volume. ADVANCES IN KNOWLEDGE: Until more refined methods are available for assessing thyroid size, both subjective and objective evaluation are recommended in CH.

A Novel Homozygous Mutation in the Solute Carrier Family 26 Member 7 Gene Causes Thyroid Dyshormonogenesis in a Girl with Congenital Hypothyroidism.

We investigated the genetic cause of thyroid dyshormonogenesis in a girl with congenital hypothyroidism. Genetic analysis showed that she was homozygous for a hitherto not described mutation (c.1432_1433delGT, p.V478KfsX11) in the solute carrier family 26 member 7 (SLC26A7) gene. SLC26A7 is proposed to be an anion transporter in the thyroid gland. The mutation leads to a frameshift and a premature stop codon. The predicted protein is truncated and very likely to be nonfunctional if it was expressed at all. In addition, in silico studies predict the mutation to be pathogenic.

Identification of Transient Receptor Potential Channel 4-Associated Protein as a Novel Candidate Gene Causing Congenital Primary Hypothyroidism.

BACKGROUND: Congenital primary hypothyroidism (CH) is the most common endocrine disorder in neonates. METHODS: To identify novel genes, we performed whole exome sequencing (WES) in 6 patients with CH due to thyroid dysgenesis (TD). The potential effects of the most relevant variants were analyzed using in silico prediction tools. The most promising candidate gene, transient receptor potential channel 4-associated protein (TRPC4AP), was sequenced in 179 further patients with TD. Expression of TRPC4AP in human thyroid was investigated using RT-PCR. Trpc4ap- functional analysis was performed in Xenopus laevis using Morpholino (MO) antisense oligomers. RESULTS: WES identified a likely damaging mutation in TRPC4AP leading to a de novo stop codon p.Q552*. Targeted sequencing of TRPC4AP demonstrated gene variants with predicted damaging potential in 5 patients resulting each in an amino acid exchange (p.P706S, p.F729L, p.S777C, and p.N229S). We demonstrated that TRPC4AP is expressed in human thyroid gland tissue. Using Xenopus laevis, we showed that the volume of the tadpole thyroid anlage was reduced by 20% in Trpc4ap MO knockdowns compared to controls and by 41% in "Clustered Regularly Interspaced Short Palindromic Repeats"/Cas9-mediated gene knockout experiments. DISCUSSION: A recognized interaction of TRPC4AP and the NF-kappa-B-essential-modulator encoded by IKBKG gene was identified by IPA analysis. IKBKG plays a role in activation of the NF-κB-signaling pathway and regulates genes involved in proliferation and survival of thyrocytes and expression of key enzymes of thyroid hormone synthesis. CONCLUSION: TRPC4AP was identified as a novel candidate gene in TD, but further studies are needed to validate its role in thyroid function.

Novel Mutations in the NKX2.1 gene and the PAX8 gene in a Boy with Brain-Lung-Thyroid Syndrome.

OBJECTIVE: To elucidate the molecular mechanism which causes thyroid dysgenesis (TD) in a boy with brain-lung-thyroid syndrome. DESIGN, PATIENTS, MEASUREMENTS: We describe a patient with TD, respiratory disease and cerebral palsy who is heterozygous for mutations in two different genes, the PAX8 (p.E234K) and the NKX2.1 (p.A329GfsX108). In vitro studies were performed to functionally characterize these mutations. Congenital hypothyroidism (CH) was identified by neonatal screening associated with a hypoplastic thyroid gland. Postpartum he developed a brain-lung-thyroid syndrome with severe respiratory failure, symptomatic epilepsy and a considerable psychomotor retardation. The DNA-binding capability and the transcriptional activity of the two mutated transcription factors were investigated in vitro. RESULTS: The NKX2.1 mutation did not show any transcriptional activity and had almost no DNA-binding. The PAX8 mutation was normally located to the nucleus and showed a normal transactivation and a normal binding to the known downstream targets. CONCLUSIONS: The molecular defect explaining the phenotype of brain-lung-thyroid syndrome was identified. To what extent the PAX8 mutation contributes to the phenotype needs to be further investigated. We recommend to screen patients with CH and TD for mutations in all known TD candidate genes.

A further case of brain-lung-thyroid syndrome with deletion proximal to NKX2-1.

Brain-lung-thyroid syndrome (OMIM #610978) is associated with mutations in the NK2 homeobox 1 (NKX2-1) gene, a transcription factor important in development. 50% of patients are affected by the full triad, comprising congenital hypothyroidism, benign hereditary chorea and infant respiratory distress syndrome. Four cases have previously been reported where a patient has features consistent with brain-lung-thyroid syndrome and a chromosome 14q13 deletion adjacent to, but not disrupting, NKX2-1. We present a patient who has a phenotype consistent with brain-lung-thyroid syndrome, featuring congenital hypothyroidism and choreoathetoid movements with gross motor delay. Thyroid ultrasound showed a small-normal gland and spontaneous resolution of hypothyroidism. Array CGH revealed a de novo 14q13.2-3 deletion adjacent to but not directly involving NKX2-1. Sequencing of NKX2-1 was normal. This report highlights a further case of chromosomal deletion adjacent to NXK2-1 in a patient with a phenotype consistent with brain-lung-thyroid syndrome, and confirms that array-CGH is a useful test in the investigation of congenital hypothyroidism. Deletion of the adjacent gene MBIP in most reported cases so far may be relevant to the pathogenesis of brain-lung-thyroid syndrome. Deletion of nearby promoter or enhancer elements acting on NKX2-1 could also be an important factor. However, further work is needed to elucidate the pathogenesis of the brain-lung-thyroid phenotype in such cases.

Familial Central Hypothyroidism Caused by a Novel IGSF1 Gene Mutation.

BACKGROUND: Congenital hypothyroidism of central origin (CH-C) is a rare disease in which thyroid hormone deficiency is caused by insufficient thyrotropin stimulation of a normal thyroid gland. A recently described syndrome of isolated CH-C and macroorchidism was attributed to loss-of-function mutations of the immunoglobulin superfamily, member 1 gene (IGSF1). PATIENTS AND METHODS: CH-C was diagnosed in three siblings. The TRH, TRHR, and TSHB genes were sequenced followed by whole-exome sequencing in the proband. A mutation identified in IGSF1 was analyzed by direct PCR sequencing in family members. The effects of the mutation were assessed by in vitro studies in HEK293 cells. RESULTS: The index case was negative for mutations in TRH, TRHR, and TSHB. Whole-exome sequencing revealed a novel insertion mutation in IGSF1, c.2284_2285insA, p.R762QfsX7, which was confirmed by direct PCR sequencing and was identified in six additional family members. The mutation introduces a frame-shift and premature stop codon in the seventh Ig loop, thereby truncating IGSF1. In vitro studies revealed that the mutated IGSF1-R762QfsX7 migrates as a doublet at ∼28 kDa, which is far smaller than the wild type protein (130-140 kDa). Both bands were endonuclease H sensitive, indicating immature glycosylation and failure of the protein to traffic out of the endoplasmic reticulum to the plasma membrane. Further phenotypic findings in the family included macroorchidism and infertility in the uncle and mild neurological phenotypes in the affected males, such as hypotonia, delayed psychomotor development, clumsy behavior, and attention deficit disorder. CONCLUSIONS: We identified a novel insertion mutation in the IGSF1 gene and further delineated the phenotype of the IGSF1-deficiency syndrome. Our findings indicate a possible association between an IGSF1 mutation and neurological phenotypes.

A novel deletion in the thyrotropin Beta-subunit gene identified by array comparative genomic hybridization analysis causes central congenital hypothyroidism in a boy originating from Turkey.

BACKGROUND: Isolated central congenital hypothyroidism (ICCH) is rare but important. Most ICCH patients are diagnosed later, which results in severe growth failure and intellectual disability. OBJECTIVE: We describe a boy with ICCH due to a large homozygous TSHß gene deletion. RESULTS: A 51-day-old male Turkish infant, whose parents were first cousins, was admitted for evaluation of prolonged jaundice. His clinical appearance was compatible with hypothyroidism. Venous thyrotropin (TSH) was undetectably low, with a subsequent low free T4 and a low free T3, suggestive of central hypothyroidism. Using different PCR protocols, we could not amplify both coding exons of the boy's TSHß gene, which suggested a deletion. An array comparative genomic hybridization (aCGH) using specific probes around the TSHß gene locus showed him to be homozygous for a 6-kb deletion spanning all exons and parts of the 5' untranslated region of the gene. CONCLUSIONS: Infants who are clinically suspected of having hypothyroidism should be evaluated thoroughly, even if their TSH-based screening result is normal. In cases with ICCH and undetectably low TSH serum concentrations, a TSHß gene deletion should be considered; aCGH should be performed when gene deletions are suspected. In such cases, PCR-based sequencing techniques give negative results.

A new mutation in the promoter region of the PAX8 gene causes true congenital hypothyroidism with thyroid hypoplasia in a girl with Down's syndrome.

BACKGROUND: Thyroid dysfunction is common in newborn infants with Down's syndrome (DS), but defects causing classic thyroid dysgenesis (TD) with permanent congenital hypothyroidism (CH) have not been described. OBJECTIVE: We studied a girl with DS and CH who had a mutation in the promoter sequence of the PAX8 gene. RESULTS: A female infant was found to have trisomy 21 and CH, with a venous thyrotropin (TSH) of >150 mU/L and a free thyroxine (fT4) of 15.1 pmol/L (day 12). Thyroid peroxidase antibodies and thyroglobulin antibodies were elevated. Scintigraphy showed normal uptake, but ultrasound identified a small gland with heterogenous echotexture and cystic changes. Sequence analysis of the PAX8 gene revealed a new heterozygous maternally inherited mutation (-3C>T) close to the transcription initiation site. Electromobility shift assay studies of the wild type and the mutant PAX8 sequence incubated with nuclear extracts from PCCL3 cells exhibited that the sequence at position -3 is not involved in specific protein binding. However, the mutant PAX8 promoter showed a significantly reduced transcriptional activation of a luciferase reporter gene in vitro tested in HEK, PCCL3, as well as in HeLa cells, indicating that this mutation is very likely to lead to reduced PAX8 expression. CONCLUSIONS: The persistent CH in this patient with DS is likely to be attributable to the diminished PAX8 expression due to a new heterozygous mutation in the PAX8 promoter sequence. Our case shows that true CH may occur in DS, as in the general population. Furthermore, it is possible that the trisomy 21 itself may have resulted in a more severe phenotypic expression of the PAX8 mutation in the child than the mother.

Diagnostic and predictive value of ultrasound and isotope thyroid scanning, alone and in combination, in infants referred with thyroid-stimulating hormone elevation on newborn screening.

OBJECTIVE: To determine the diagnostic and predictive value of ultrasound and radioisotope scans of the thyroid, alone and in combination, during a single visit after initial referral by the screening laboratory with thyroid-stimulating hormone (TSH) elevation. STUDY DESIGN: Retrospective blind review of ultrasound and radioisotope images followed by final diagnosis based on clinical features, biochemistry, imaging, and molecular genetic study. RESULTS: Infants (n = 97; 61 female) with median birthweight 3.38 kg (range 2.04-4.86) and gestation 40 weeks (range 33-42), underwent successful dual thyroid ultrasound and technetium-99m pertechnetate radioisotope scan in a single center. Combined scanning at the initial visit resulted in a correct final diagnosis in 79 of 97 (81%) cases. One patient was misdiagnosed initially as having athyreosis as the result of delayed radioisotope scan and the diagnosis of ectopia made later on diagnostic challenge. The specificity/sensitivity for radioisotope scan and for ultrasound was as follows: 100%/97% and 100%/55% for ectopia (n = 39); 81%/100% and 54%/100% for athyreosis (n = 18); and 89%/90% and 80%/95% for dyshormonogenesis (n = 20). Neither modality, alone or in combination, predicted final diagnosis in eutopic glands due to hypoplasia (n = 4), transient TSH elevation (n = 12), and status still uncertain (n = 4). CONCLUSION: More than 80% of newborn infants with TSH elevation can be diagnosed correctly on initial imaging with combined radioisotope scan and ultrasound. Ultrasound cannot reliably detect thyroid ectopia. Radioisotope scan, especially if performed late, may show no uptake despite the presence of a eutopic gland.

A new PAX8 mutation causing congenital hypothyroidism in three generations of a family is associated with abnormalities in the urogenital tract.

BACKGROUND: Although thyroid dysgenesis is the most common cause of congenital hypothyroidism (CH), its molecular basis remains largely elusive. Indeed, in only a minority of cases with thyroid dysgenesis (2%-3%) was it possible to identify an underlying genetic defect. The objective of this study was to screen the PAX8 gene and the PAX2 gene in a family with six cases of CH spanning three generations and presenting urogenital malformations. Herein, we report a case series and in vitro characterization of the PAX8 gene mutation. METHODS: Investigations were conducted at a tertiary care referral center. The index case was diagnosed to have congenital hypothyroidism at 7 months of age when he presented with severe impairment of suckling, constipation, and poor development. Treatment with levothyroxine corrected the symptoms and was associated with catch-up growth. His progeny, including two sons, one daughter, and two granddaughters, were affected by CH, and three of them received the diagnosis at neonatal screening. Ultrasound demonstrated normally located thyroid glands with reduced volumes. Five of the six affected family members, including the index case, had urogenital malformations, including incomplete horseshoe kidney, undescended testicles, hydrocele, and ureterocele. Strabismus was found in three out of six affected patients. No other somatic malformations were found. RESULTS: Direct sequencing of the PAX8 gene revealed a new heterozygous mutation (c.74C > G) in all affected individuals. This mutation leads to substitution of proline with arginine at codon 25 (P25R). Fluorescence microscopy showed that P25R is normally located in the nucleus. In transient transfection studies, this mutation causes reduced transcriptional activation ability when using a luciferase reporter construct under the control of a thyroglobulin promoter. This diminished transactivation ability is due to loss of DNA binding capability as shown in electrophoresis mobility shift assay. The sequencing analysis of the PAX2 gene was normal. CONCLUSIONS: We conclude that this novel PAX8 mutation is responsible for a severe form of dominantly inherited CH. The mutation seems to be associated with abnormalities of the urogenital tract.

A clinically euthyroid child with a large goiter due to a thyroglobulin gene defect: clinical features and genetic studies.

A 10-year old child born to consanguineous parents presented with an extremely large goiter, a low free T4 level and free T4 index, and normal TSH concentration. The findings of undetectable thyroglobulin (TG) and low free T4, and an elevated free T3/free T4 ratio suggested the possibility of a defect in TG synthesis. Noteworthy aspects of this case were the extremely elevated thyroidal radioiodide uptake despite a normal TSH concentration and the fact that the reduction in the size of her goiter only occurred when her TSH was suppressed below the normal range. Gene sequencing revealed that the patient was homozygous for a donor splice site mutation in intron 30 (IVS30+1G>C). Isolation of RNA obtained from the thyroid gland by fine needle aspiration and sequencing of the TG cDNA confirmed the prediction that exon 30 was skipped, resulting in an in-frame loss of 46 amino acids.

Novel heterozygous thyrotropin receptor mutation presenting with neonatal hyperthyrotropinaemia, mild thyroid hypoplasia and absent uptake on radioisotope scan.

Hyperthyrotropinaemia [mildly elevated thyrotropin (TSH) with normal thyroxine (T4) levels] demands a full assessment, including clinical examination, thyroid imaging and, where indicated, molecular genetic investigations. A male infant, both of whose parents were on T4 treatment, was referred at age 57 days with mild but persistent TSH elevation (12.7 mU/L) and normal free T4 (19.6 pmol/L), following notification by the screening laboratory of a capillary TSH of 10.7 mU/L (reference range, 1.7-9.1 mU/L) on day 8. Assessment showed a venous free T4 level of 15 pmol/L, venous TSH of 20.9 mU/L, serum thyroglobulin of 63 µg/L (reference range, <50 µg/L), and negative thyroglobulin and thyroid peroxidase antibodies. Thyroid ultrasound showed a eutopic, slightly small gland with heterogeneous texture; however, there was no uptake on radioisotope scan. Molecular genetic studies demonstrated a novel missense heterozygous mutation in the TSH receptor (TSHR) gene (c.1169G>T;p.Cys390Phe) in the child, mother and maternal grandmother, but not in the father. The infant was treated with T4 but this was discontinued at age 3 years when repeat testing showed a free T4 of 16.7 pmol/L (reference range, 9-23 pmol/L) and TSH of 8.5 mU/L (reference range, 0.3-5.5 mU/L). A heterozygous TSHR mutation should be considered in the context of hyperthyrotropinaemia and reduced/absent uptake on radioisotope scan. Detection of this mutation has allowed our patient to discontinue T4 treatment for the moment, with a view to staying off treatment in the long-term.

Two cases of thyroid dysgenesis caused by different novel PAX8 mutations in the DNA-binding region: in vitro studies reveal different pathogenic mechanisms.

BACKGROUND: Mutations in PAX8, a transcription factor gene, cause thyroid dysgenesis (TD). The extreme variability of the thyroid phenotype makes it difficult to identify individuals harboring PAX8 gene mutations. Here we describe two patients with TD and report two novel PAX8 gene mutations (S54R and R133Q). We performed in vitro studies to functionally characterize these mutations. METHODS: Using PAX8 expression vectors, we investigated whether the PAX8 mutants localized correctly to the nucleus. To analyze the DNA-binding properties of S54R and R133Q, electrophoretic mobility shift assays were performed. Furthermore, we measured whether the mutant PAX8 proteins were able to activate the thyroglobulin (TG)- and the thyroperoxidase (TPO)-promoters. RESULTS: S54R had an impaired binding to DNA and a negligible activity on the TG- and the TPO-promoters. The DNA-binding property of R133Q, which is located in the highly conserved terminal portion of the PAX8 DNA-binding domain, was normal. Interestingly, it also exhibited dramatically impaired activation of the TG- and TPO-promoters. However, R133Q has no dominant negative effect on the WT protein in vitro. Thus, the underlying molecular mechanism by which the function of R133Q is impaired remains to be elucidated. CONCLUSIONS: We identified and functionally characterized two novel mutations of the PAX8 gene that lead to TD by distinct mechanisms. A structural defect of the mutant R133Q leading to a reduced capability for induced fit upon DNA interaction might explain the disparity between its apparently normal binding to DNA, but lack of promoter activation.

A cross-sectional single-centre study on the spectrum of Pompe disease, German patients: molecular analysis of the GAA gene, manifestation and genotype-phenotype correlations.

BACKGROUND: Pompe disease (Glycogen storage disease type II, GSD II, acid alpha-glucosidase deficiency, acid maltase deficiency, OMIM # 232300) is an autosomal-recessive lysosomal storage disorder due to a deficiency of acid alpha-glucosidase (GAA, acid maltase, EC 3.2.1.20, Swiss-Prot P10253). Clinical manifestations are dominated by progressive weakness of skeletal muscle throughout the clinical spectrum. In addition, the classic infantile form is characterised by hypertrophic cardiomyopathy. METHODS: In a cross-sectional single-centre study we clinically assessed 3 patients with classic infantile Pompe disease and 39 patients with non-classic presentations, measured their acid alpha-glucosidase activities and analysed their GAA genes. RESULTS: Classic infantile patients had nearly absent residual enzyme activities and a typical clinical course with hypertrophic cardiomyopathy until the beginning of therapy. The disease manifestations in non-classic patients were heterogeneous. There was a broad variability in the decline of locomotive and respiratory function. The age of onset ranged from birth to late adulthood and correlated with enzyme activities. Molecular analysis revealed as many as 33 different mutations, 14 of which are novel. All classic infantile patients had two severe mutations. The most common mutation in the non-classic group was c.-32-13T>G. It was associated with a milder course in this subgroup. CONCLUSIONS: Disease manifestation strongly correlates with the nature of the GAA mutations, while the variable progression in non-classic Pompe disease is likely to be explained by yet unknown modifying factors. This study provides the first comprehensive dataset on the clinical course and the mutational spectrum of Pompe disease in Germany.

A new heterozygous mutation (D196N) in the Gs alpha gene as a cause for pseudohypoparathyroidism type IA in a boy who had gallstones.

BACKGROUND: Pseudohypoparathyroidism (PHP) is characterized by hypocalcemia and hyperphosphatemia in association with an increased secretion of parathyroid hormone (PTH) due to decreased target tissue responsiveness to PTH. Patients with PHP type Ia are not only resistant to PTH, but also to other hormones that bind to receptors coupled to stimulatory G protein (Gsalpha). PHP Ia and Albright hereditary osteodystrophy (AHO) are caused by a reduced activity of the Gsalpha protein. Heterozygous inactivating Gs alpha (GNAS) gene mutations have been identified in these patients. METHODS: We studied a boy with PHP Ia. During follow-up the patient developed elevated liver enzyme serum levels and abdominal discomfort. Gsalpha activity was measured in erythrocyte membranes from the patient and the GNAS coding region of Gsalpha sequenced. RESULTS: Gsalpha activity was reduced (62%) and molecular analysis revealed a new heterozygous GNAS gene mutation (D196N). Gallstones were diagnosed and cholecystectomy was performed. Biochemical analysis revealed cholesterol stones, a condition that was not reported before in PHP Ia. CONCLUSIONS: Cholesterol gallstones may rarely be associated with PHP Ia and should be taken into account.

Mutations in the NKX2.5 gene and the PAX8 promoter in a girl with thyroid dysgenesis.

CONTEXT: Screening of the known candidate genes involved in thyroid organogenesis has revealed mutations in a small subset of patients with congenital hypothyroidism due to thyroid dysgenesis (TD). OBJECTIVE: We studied a girl with TD who had mutations in two transcription factors involved in thyroid development. RESULTS: Sequencing analysis of candidate genes involved in thyroid gland development revealed a new paternally inherited heterozygous mutation in the NKX2.5 gene (S265R) and a new maternally inherited heterozygous mutation in the PAX8 promoter region (-456C>T). Both parents and a brother, who was also heterozygous for both mutations, were phenotypically normal. Immunofluorescence microscopy showed a correct nuclear localization of both wild-type (WT) and mutant NKX2.5 proteins. EMSA demonstrated that the mutant NKX2.5 binds to the NKE_2, DIO2, TG, and TPO promoter elements equally well as the WT protein. However, the mutant NKX2.5 protein showed a 30-40% reduced transactivation of the thyroglobulin and the thyroid peroxidase promoters and a dominant-negative effect of the mutant NKX2.5. EMSA studies of the WT and mutant PAX8 promoter sequences incubated with nuclear extracts from PCCL3 cells exhibited a loss of protein binding capacity of the mutant promoter. In addition, the mutant PAX8 promoter showed a significantly reduced transcriptional activation of a luciferase reporter gene in vitro. Thus, this promoter mutation is expected to lead to reduced PAX8 expression. CONCLUSIONS: We identified new heterozygous mutations in both NKX2.5 and PAX8 genes of a girl with TD. Both defects might contribute to the phenotype.

A single copy of the recently identified dual oxidase maturation factor (DUOXA) 1 gene produces only mild transient hypothyroidism in a patient with a novel biallelic DUOXA2 mutation and monoallelic DUOXA1 deletion.

CONTEXT: Dual oxidases (DUOX1 and DUOX2) play a crucial role in the generation of hydrogen peroxide required in the oxidation of iodide and the synthesis of thyroid hormone. Heterodimerization with specific maturation factors (DUOXA1 and DUOXA2) is essential for the maturation and function of the DUOX enzyme complexes. Biallelic loss-of-function mutations of DUOX2 result in congenital hypothyroidism (CH), whereas a single reported case of homozygous DUOXA2 mutation (Y246X) has been associated with mild CH. OBJECTIVE: We now report an infant with transient CH due to a complex genetic alteration of the DUOX/DUOXA system. RESULTS: Our patient was born to euthyroid nonconsanguineous parents and presented with an elevated TSH and enlarged thyroid gland at neonatal screening. Genetic analysis revealed a missense mutation (C189R) on the maternal DUOXA2 allele. The mutant DUOXA2 protein showed complete loss-of-function in reconstituting DUOX2 in vitro. The apparent C189R homozygosity of the proband in the absence of the same mutation in the father led to detailed gene mapping, revealing an approximately 43-kb pair deletion encompassing DUOX2, DUOXA1, and DUOXA2. Thus, in addition to being deficient in DUOXA2, the proband lacks one allele of DUOX2 and DUOXA1 but has two functioning DUOX1 alleles. CONCLUSION: The transient CH in the presence of only one functional maturation factor allele indicates a high level of functional redundancy in the DUOX/DUOXA system.

Viperin mRNA is a novel target for the human RNase MRP/RNase P endoribonuclease.

RNase MRP is a conserved endoribonuclease, in humans consisting of a 267-nucleotide RNA associated with 7-10 proteins. Mutations in its RNA component lead to several autosomal recessive skeletal dysplasias, including cartilage-hair hypoplasia (CHH). Because the known substrates of mammalian RNase MRP, pre-ribosomal RNA, and RNA involved in mitochondrial DNA replication are not likely involved in CHH, we analyzed the effects of RNase MRP (and the structurally related RNase P) depletion on mRNAs using DNA microarrays. We confirmed the upregulation of the interferon-inducible viperin mRNA by RNAi experiments and this appeared to be independent of the interferon response. We detected two cleavage sites for RNase MRP/RNase P in the coding sequence of viperin mRNA. This is the first study providing direct evidence for the cleavage of a mRNA by RNase MRP/RNase P in human cells. Implications for the involvement in the pathophysiology of CHH are discussed.

Non-immune goiter and hypothyroidism in a 19-week fetus: a plea for conservative treatment.

Hypothyroidism was documented by cordocentesis at 19 weeks in a fetus with non-immune goiter. Intra-amniotic thyroxine was injected at 25 weeks when amniotic fluid volume increased. Psychomotor outcome was normal. We argue that intra-amniotic thyroxine should not be used to treat the hypothyroidism but only to correct the development of polyhydramnios.

Refinement of the 12q14 microdeletion syndrome: primordial dwarfism and developmental delay with or without osteopoikilosis.

In their studies on the molecular basis of osteopoikilosis, Menten et al have identified three individuals with microdeletions on chromosome 12q14.4, which removed several genes including LEMD3, the osteopoikilosis gene. In addition to osteopoikilosis, affected individuals had growth retardation and developmental delay. We now report a smaller 12q14.4 microdeletion in a boy with severe pre and postnatal growth failure, and mild developmental delay; the patient was small at birth and presented with poor feeding and failure to thrive during the first 2 years of life, similar to the phenotype of primordial dwarfism or severe Silver-Russell syndrome (SRS). The 12q14 deletion did not include LEMD3, and no signs of osteopoikilosis were observed on skeletal radiographs. Among the deleted genes, HMGA2 is of particular interest in relationship to the aberrant somatic growth in our patient, as HMGA2 variants have been linked to stature variations in the general population and loss of function of Hmga2 in the mouse results in the pygmy phenotype that combines pre and postnatal growth failure, with resistance to the adipogenic effect of overfeeding. Sequencing of the remaining HMGA2 allele in our patient showed a normal sequence, suggesting that HMGA2 haploinsufficiency may be sufficient to produce the aberrant growth phenotype. We conclude that the 12q14.4 microdeletion syndrome can occur with or without deletion of LEMD3 gene; in LEMD3-intact cases, the phenotype includes primordial short stature and failure to thrive with moderate developmental delay, but osteopoikilosis is absent. Such cases will likely be diagnosed as Silver-Russell-like or as primordial dwarfism.