Phenotypic homogeneity and genotypic variability in a large series of congenital isolated ACTH-deficiency patients with TPIT gene mutations

CONTEXT

Congenital isolated ACTH deficiency (IAD) is a rare disease characterized by low plasma ACTH and cortisol levels and preservation of all other pituitary hormones. This condition was poorly defined before we identified TPIT, a T-box transcription factor with a specific role in differentiation of the corticotroph lineage in mice and humans, as its principal molecular cause.

OBJECTIVE

We have enlarged our series of IAD patients to better characterize the phenotype and the genotype of this rare disease.

DESIGN

Each exon of the TPIT gene was amplified and sequenced in IAD patients without any identified cause. A functional analysis of each new TPIT mutation was performed.

RESULTS

We described the largest series of 91 IAD patients and identified three distinct groups: neonatal onset complete or partial IAD or late onset IAD. We did not identify any TPIT mutation in patients with partial or late-onset IAD. However, we found a TPIT mutation in 65% of patients with neonatal-onset complete IAD. These patients are homozygous or compound heterozygous for TPIT mutations, and their parents are healthy heterozygous carriers. We identified nine new mutations: four missense, one one-nucleotide deletion, three splice-site mutations, and one large deletion. TPIT mutations lead to loss of function by different mechanisms, such as non-sense-mediated mRNA decay, abnormal mRNA splicing, loss of TPIT DNA binding or protein-protein interaction defects.

CONCLUSION

TPIT mutations are responsible for two thirds of neonatal-onset complete IAD but can not be detected in partial or late-onset IAD.

Variations of the paranasal sinuses in Melanesians as observed by CT

Studies have reported the incidence of anatomical variants of the paranasal sinuses for specific populations with a view to helping surgeons avoid possible complications during functional endoscopic sinus surgery. Some have found significant variation when comparing different populations. The current study has used computed tomography (CT) scans to observe variations in the paranasal sinuses in a non-random sample of museum skulls of Melanesians, a racial group that has not previously been studied in this respect. The incidence of variants found were: agger nasi cells 59.5%, concha bullosa 41.5%/o, Haller's air cells 31.7%, internal carotid artery bulge in the sphenoid sinus 23.8%/, supraorbital cells 16. 7%, paradoxical curvature of the mid-dle turbinate 7.5% and pneumatization of crista galli 7.1%.Because of contradictory findings in the literature as to the incidence of such variations between racial groups the authors are able to make only limited meaningful comparisons between their subjects and other such groups.

Screening of SLC26A4 (PDS) gene in Pendred's syndrome: a large spectrum of mutations in France and phenotypic heterogeneity

Sensorineural hearing defect and goiter are common features of Pendred's syndrome. The clinical diagnosis of Pendred's syndrome remains difficult because of the lack of sensitivity and specificity of the thyroid signs. The identification of PDS as the causative gene allowed molecular screening and enabled a re-evaluation of the syndrome to identify potential diagnostic characteristics. This report presents the clinical and genotypic findings of 30 French families, for whom a diagnosis of Pendred's syndrome had been made. Twenty-seven families had at least one mutated allele. Twenty-eight different mutations were identified, 11 of which had never been previously reported. The main clinical characteristics were: early hearing loss, fluctuation in terms of during deafness evolution, and the presence of an enlarged vestibular aqueduct.

Hypogonadotrophic hypogonadism associated with prelingual deafness due to a connexin 26 gene mutation

In Mediterranean countries, almost half the incidence of non-syndromic congenital hearing loss is caused by mutations in the gap junction (GJ) connexin 26 gene (GJB2/DFNB1 locus). In this form of deafness the cochlear defect is usually isolated. We describe here the first case of hypogonadotrophic hypogonadism in association with this particular cochlear defect. The male patient had moderate deafness inherited from his deaf parents. All family members had a homozygous 35delG mutation in the connexin 26 gene. This mutation accounts for 70% of all connexin 26 gene mutations. The patient was referred to a paediatric endocrinology unit at 11 years of age for moderate growth retardation. Growth rate was normal until 11 years. The patient then presented delayed puberty (testicular volume 4 ml, penis length 4 cm) and did not undergo the usual pubertal growth spurt. LH and FSH secretory responses to GnRH at the age of 14.5 years (bone age 13.5 years), were: LH baseline level 1.1 IU/l, peak 34 IU/l; FSH baseline level 1.8 IU/l, peak 5.7 IU/l. Testosterone concentration was <0.11 ng/ml. From 11 to 14 years old, testosterone concentration ranged from 0.11 to 0.2 ng/ml. Anti-Mullerian hormone (AMH) level was 38.6 ng/ml (normal for Tanner stage I), cortisol 109 ng/ml, and ACTH 37 pg/ml., Karyotype was 46 XY. On MRI analysis, the anterior pituitary and olfactory bulbs were normal. These data were consistent with partial hypogonadotrophic hypogonadism of hypothalamic origin, and the patient was treated with testosterone. This report supports the possible involvement of connexins in puberty initiation. Connexins may play a part in the co-ordination and synchronisation of GnRH release.

IGF type 1 receptor ligand binding characteristics are altered in a subgroup of children with intrauterine growth retardation

The IGFs, IGF-I and IGF-II, regulate fetal growth by activating IGF type 1 receptors (IGF-IR). We aimed to quantify the binding of IGF-I to its cognate receptors in intrauterine growth-retarded children (IUGR). We measured the affinity of the erythrocyte IGF-IR and the number of IGF-IR receptors in 17 children with retarded growth (mean height, -2.7 SD), normal levels of GH, and a history of idiopathic intrauterine growth retardation (height at birth, -10 to -2 SD; mean, -3.1 SD). These children had reduced receptor affinity (Kd = 0.47 nM; P < 0.01) and more receptors per cell [binding capacity (Bmax) = 11.7 binding sites/cell; P < 0.05)] compared with control children (Kd = 0.32 nM; Bmax = 7.8 binding sites/cell). Moreover, the distributions of Kd and Bmax suggested that there were two groups of IUGR children. Group 1 included subjects with normal receptor binding function (Kd = 0.36 nM; Bmax = 8.2 sites/cell) and normal levels of circulating IGF-I. Group 2 comprised children with low receptor affinity (Kd = 0.56 nM) and increased receptor number (Bmax = 14.7 sites/cell). This group showed significantly decreased IGF-I levels (-2.1 SD; P < 0.01). We investigated these IGF-IR binding parameters in two additional groups of growth-retarded children (Turner syndrome and patients with chronic renal failure), in whom the IGF-I axis was not believed to be the primary cause, and found that Kd and Bmax were normal or nearly normal. We also measured IGF-IR binding parameters in 4 Seckel syndrome patients with IUGR and severely retarded growth (mean height, -7.9 SD). Their receptor affinity was reduced, but not statistically different, from that in controls, and their receptor number was normal, whereas IGF-I levels were elevated. Our results suggest heterogeneous alterations in IGF-IR binding function in IUGR patients.

Insulin-like growth factor-I (IGF-I), insulin-like growth factor binding proteins (IGFBP) and insulin-like growth factor type I receptor in children with various status of chronic renal failure

Chronic renal failure in childhood causes severe growth retardation. The aim of the study was to identify whether changes in the IGF system could account for the growth retardation observed in children with chronic renal failure. Insulin-like growth factor (IGF-I) serum concentrations, insulin-like growth factor binding proteins (IGFBP) and/or IGF-I binding to erythrocyte type I receptor of IGF were analysed in 69 children (mean age 11.6 +/- 4.3 years) with chronic renal failure and growth retardation (mean height -2.6 +/- 1.8 SD). The study population was separated into three groups, according to their renal status, children on conservative treatment (CRF group: n = 30), on haemodialysis (ESRD group: n = 26) and those transplanted (RT group: n = 13). Nineteen of these children, some from each of the three groups, received recombinant growth hormone therapy (rhGH). Mean basal IGF-I serum concentrations were -0.7 +/- 1.2 SD in the CRF group, + 2.1 +/- 3 SD in the ESRD group and + 1.1 +/- 2 SD in the RT group. Under rhGH therapy, as height velocity improved, mean IGF-I concentrations increased up to + 3.1 +/- 0.6 SD in the CRF group, to + 6.9 +/- 2.8 SD in the ESRD group and to + 3.9 +/- 2 SD in the RT group. Basal IGFBP-3 levels, studied by Western Ligand Blot were low in the CRF group and high in the ESRD and normal in the RT groups, whereas IGFBP-2 and a 30-32 kDa IGFBP were always high in all cases. Western immunoblot analysis showed that this 30-32 kDa IGFBP was mostly composed of IGFBP-1 and IGFBP-6 in all three groups, but IGFBP-6 was particularly abundant in the ESRD group. IGFBP-6 concentrations assessed by RIA were moderately increased in CRF children (392 +/- 177 ng/mL) and very high in children on ESRD (2094 +/- 1525 ng/mL) when compared to normal values (131 +/- 42 ng/mL). Binding studies of IGF type I receptor showed that there was no particular difference in IGF-I binding between renal failure patients and normal children. In poorly growing children, especially in ESRD children and to a lesser extent in RT children, high concentrations of IGF-I and IGFBP-1, 2, 3 and 6, suggest a resistance mainly by a sequestration mechanism. Moreover, in the CRF group, especially in the younger children, low levels of IGF-I and IGFBP-3 are evocative of an associated resistance at the GH receptor level.

[Physiopathology of the somatotropin axis in chronic renal insufficiency]

Many factors contribute to the growth failure of chronic renal failure: water and electrolytes disturbances, hypertonicity, phosphate or calcium wasting, secondary hyperparathyroidism, anemia, hypertension, metabolic acidosis, and malnutrition. In addition, the pubertal growth spurt is usually stunted. Growth hormone (GH) resistance is observed with low GH binding protein (GHBP) level, and normal or low IGF I levels despite elevated GH level. Elevated IGFBP levels may contribute to a reduced IGF activity, especially in dialysed patients. Glucocorticoid therapy in transplanted patients further contribute to poor growth and inhibited IGF I activity. As conventional treatments have a limited effect to improve growth, adult height is often far below -2 SD. GH therapy has proved to be successful, especially in young children, overpassing the hormonal resistance so that an adult height within the normal range may be reached.

The cortisol-cortisone shuttle in children born with intrauterine growth retardation

We evaluated the involvement of a possible dysfunction of 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) in the fetal growth retardation and poor growth rates of children born with intrauterine growth retardation (IUGR). Children with IUGR have a nephron deficit and are also at risk of developing cardiovascular diseases, high blood pressure, glucose intolerance, and dyslipidemia later in life. The major site of 11beta-HSD2 production is the kidney and its deficit causes hypertension. We investigated plasma concentrations of cortisol (F) and cortisone (E) and the F/E ratio in 26 control children and in 40 IUGR children without catch-up growth. We also determined cholesterol, HbA1C, insulin, and glucose levels in plasma. Mean F values were 106 +/- 54.2 ng/mL in control children and 114.6 +/- 53.2 ng/mL in IUGR children. Mean E values were 19.5 +/- 7.1 ng/mL in control children and 17.9 +/- 6.85 ng/mL in IUGR children. The mean F/E ratio for control children was 5.5 +/- 1.7. Eight (20%) of the IUGR children (IUGR children of group 1) had high F/E ratios more than 2 SD above the normal mean: 13.15 +/- 4.26, (p < 0.0001) as compared to control children, whereas the other 32 children (IUGR children of group 2) had normal F/E ratios: 5.40 +/- 1.43 (p = 0.68). Childhood height was significantly lower for group 1 than group 2 children (-3.63 SD and -2.92 SD, respectively: p < 0.01) and was negatively correlated with the F/E ratio (p < 0.01). Systolic blood pressure was higher for group 1 (p = 0.005) and for group 2 (p = 0.015) than for control children. The diastolic pressure in IUGR children of group 1 was higher than that in control children (p = 0.013) and slightly higher than that in group 2 (p = 0.1, ns). Cholesterol concentrations were higher in group 1 than in group 2 (p = 0.029), and controls (p = 0.017) and correlated positively with F/E (0.02 < p < 0.05). Fasting insulin concentrations were higher in group 1 than in group 2 (ns) and controls (ns). There was no difference in mean fasting glucose concentrations, or HbA1C between the three groups. Twenty percent of our children with IUGR and poor growth rates had high F/E ratios, suggesting a possible partial 11beta-HSD2 deficit. Whether these children are at high risk of developing cardiovascular diseases as adults remains to be further evaluated.

Follow up of precocious pseudopuberty associated with isolated ovarian follicular cysts

The clinical outcomes of seven girls presenting with pseudosexual precocity caused by isolated autonomous ovarian follicular cysts are presented. Six of the seven girls, aged 11 months to 6.9 years, had a unilateral ovarian cyst detected by ultrasound at the first acute episode. Plasma oestradiol was raised in only five of the cases, but all had a low response to luteinising hormone releasing hormone stimulation. Follow up lasted for up to eight years with recurrent episodes of variable frequency and severity in all seven patients. Evidence of McCune-Albright syndrome appeared later in only three patients. It could not be predicted from the initial symptoms or the clinical course. Mutations of the G(s)alpha protein leading to activation were investigated in the lymphocytes and ovarian and bone tissues of four patients. Only one patient showed a mutation in bone tissue. Close follow up with repeated searches for skeletal lesions remains necessary since the distribution of somatic mutations cannot be assessed by molecular studies. Most patients with recurrent ovarian cysts require a conservative approach.

Four families with loss of function mutations of the thyrotropin receptor

We observed four families with loss of function mutations of the TSH receptor gene. One patient had a homozygous Pro162 Ala substitution. The three other were compound heterozygotes: 1) Gln324-->Stop and Asp410 Asn2), Cys41 Ser and Phe525 Leu, 3) Cys390 Trp and Trp546-->Stop. In all patients, the plasma TSH concentration was increased, whereas T3 and T4 concentrations were normal. The TSH levels were normal in the heterozygous parents. These results confirmed the recessive character of TSH receptor defects. Expression of the various mutated receptors in transfected COS-7 cells demonstrated the impairment of their function. We studied the expression of the receptors on the cell surface by immunofluorescence, their ability to bind hormone, and their capacity to activate adenylate cyclase. Some mutations allowed us to identify sites that are especially important for receptor function. The substitution Cys390 Trp abolished high affinity hormone binding. Receptor mutated at Asp410 Asn bound the hormone normally, but failed to activate adenylate cyclase. This result underscores the role of this acidic extracellular residue, close to the first transmembrane segment, in signal transmission. The Phe525 Leu substitution also markedly impaired adenylate cyclase activation, underlining the importance of the second intracellular loop in receptor signaling.

Comparative study of brain magnetic resonance imaging findings in patients with low-tension glaucoma and control subjects

PURPOSE

To evaluate the presence of central nervous system degeneration in patients with low-tension glaucoma using magnetic resonance imaging.

METHOD

Ten patients with low-tension glaucoma and ten age-matched control subjects underwent magnetic resonance imaging. Cortical atrophy and cerebral infarcts were graded from "0" (normal) to "3," which was done subjectively by two neuroradiologists independently in a masked fashion. Midsagittal corpus callosum section was evaluated by measuring the thickness and cross-sectional area.

RESULTS

There was a significantly greater extent of cerebral infarcts in the patients with low-tension glaucoma (P = 0.02). The thickness of the body (P = 0.03) and genu (P = 0.04) of the corpus callosum were thinner in the patients with low-tension glaucoma. The corpus callosum cross-sectional area was smaller in the low-tension glaucoma group (P = 0.04). There were no significant differences in the other parameters in this study.

CONCLUSION

This study suggests a greater extent of cerebral infarcts and corpus callosum atrophy in patients with low-tension glaucoma. This may imply a greater degree of neuronal degeneration, possibly on an ischemic basis in low-tension glaucoma.

[Acute urine retention: a rare mode of revelation of cervico-dorsal syringomyelia caused by cyproheptadine]

BACKGROUND

Syringomyelia is rare in children aged less than 10 years, and bladder dysfunction is an unlikely first manifestation. This report describes a case of repeated episodes of acute urinary retention in a young girl revealing syringomyelia and Arnold-Chiari malformation.

CASE REPORT

A 2.5 year-old girl was admitted because she was suffering from acute urinary retention. Her poor appetite had been treated with cyproheptadine, a histamine type I blocking drug. Clinical investigation revealed no local cause for this bladder dysfunction except moderate spasticity of the legs. Cystography showed no vesicoureteral reflux. Because the episodes of urinary retention recurred each day, magnetic resonance imaging (MRI) was performed; this showed the typical features of syringomyelia extending from C5 to T11 plus Arnold-Chiari malformation. The cyproheptadine was discontinued and the urinary retention disappeared.

CONCLUSION

Cyproheptadine may have revealed latent neurogenic bladder in this case, although urodynamic studies, performed 3 months later, detected no bladder dysfunction.

First year evaluation of a private MRI facility

OBJECTIVE

To review the first years experience of the only private MRI facility in Australia.

METHOD

Utilisation Review.

RESULTS

1497 scans have been comprehensively analysed, with regard to the efficacy of the procedure in examining the brain, spinal cord, the lumbar region and the knee joint.

Computerized axial tomography in the pretreatment assessment of small-cell carcinoma of the bronchus

Computerized axial tomographic scans (CAT scans) of thorax and abdomen were used as part of the initial staging procedure of 50 consecutive patients with small-cell bronchogenic carcinoma (SCBC). The aims were to define the extent of the primary tumor and metastatic spread, and to compare the information obtained from CAT scans with conventional staging procedures. With CAT scanning, spread of the primary tumor was found to be far more extensive than originally believed when defined by conventional assessment. Of 35 patients conventionally staged as localized T1 or T2 tumors, 27 (77%) had their stage increased to extensive T3 disease. similarly, subcarinal lymph nodes were found in one patient when conventional methods were used (2%), but 16 patients (32%) were found when CAT scan was used. Unsuspected adrenal metastases were found in eight patients (16%) and retrocrural nodes in four patients (8%). Thirty-seven patients (74%) were found to have Stage III tumors when conventional staging was used; 47 patients (94%) were found to be Stage III following CAT scanning, demonstrating that, within the thorax, localized tumors are very uncommon. CAT scanning demonstrates the degree of intrathoracic spread very clearly, and has a valuable role in the initial investigation of patients with SCBC if the planned treatment includes radiotherapy.