Ivan McGown

The placenta in Beckwith-Wiedemann syndrome: genotype-phenotype associations, excessive extravillous trophoblast and placental mesenchymal dysplasia

Aims: Placental mesenchymal dysplasia (PMD) is a rare condition which is associated with the disparate fetal outcomes of Beckwith–Wiedemann syndrome (BWS), fetal growth restriction or intrauterine and neonatal death. We aimed to investigate the potential epigenetic/genetic anomalies associated with PMD and their relationship with the different causes of BWS. Methods: Eight archival cases in which PMD, BWS or both were diagnosed were investigated by correlating morphology with p57KIP2 expression, XY fluorescence in situ hybridisation (FISH) analysis and DNA genotyping. Results: Placentae from BWS cases caused by aberrant IC2 methylation, leading to abnormal p57KIP2 expression, did not show PMD but had a striking excess of extravillous trophoblast. PMD in the absence of BWS was caused by androgenetic/biparental mosaicism. The single case of BWS with PMD was due to mosaic uniparental disomy of 11p15.5. In the latter two aetiologies, our results indicate that the uniparental disomy is confined to the villous mesenchyme. Conclusions: These results suggest that the link between PMD and BWS is uniparental disomy of genes confined to the telomeric IC1 region of 11p15.5. A strong candidate gene is IGF2, a known growth factor of placental mesenchyme.

A novel NR5A1 variant in an infant with elevated testosterone from an Australasian cohort of 46,XY patients with disorders of sex development

NR5A1 loss‐of‐function mutations are increasingly found to be the cause of 46,XY disorders of sex development (DSD).

Autopsy Diagnosis of 21-Hydroxylase Deficiency CAH in a Case of Apparent SIDS

A 5-month-old boy with no history of vomiting, early sexual development, or noticeable significant illness was found dead in bed. Autopsy demonstrated bilateral adrenal hyperplasia unequivocally shown on biochemical testing of blood and urine to be due to 21-hydroxylase deficiency. Genetic analysis of the CYP21 gene showed compound heterozygosity; 1 allele contained a pseudogene sequence (gene conversion) and the other contained a previously described I172N point mutation. On theoretical grounds, the genotype would have been expected to cause simple virilizing congenital adrenal hyperplasia but, because no other cause of death could be found, it is possible that it caused a fatally severe loss of enzyme activity in this child. If this assumption is valid, newborn screening would have prevented this death, had it been available.

Treatment of Lesch-Nyhan disease with S-adenosylmethionine: Experience with five young Malaysians, including a girl

BACKGROUND Lesch-Nyhan disease (LND) is a rare X-linked recessive neurogenetic disorder caused by deficiency of the purine salvage enzyme hypoxanthine phosphoribosyltransferase (HPRT, EC 2.4.2.8) which is responsible for recycling purine bases into purine nucleotides. Affected individuals have hyperuricemia leading to gout and urolithiasis, accompanied by a characteristic severe neurobehavioural phenotype with compulsive self-mutilation, extrapyramidal motor disturbances and cognitive impairment. AIM For its theoretical therapeutic potential to replenish the brain purine nucleotide pool, oral supplementation with S-adenosylmethionine (SAMe) was trialed in 5 Malaysian children with LND, comprising 4 related Malay children from 2 families, including an LND girl, and a Chinese Malaysian boy. RESULTS Dramatic reductions of self-injury and aggressive behaviour, as well as a milder reduction of dystonia, were observed in all 5 patients. Other LND neurological symptoms did not improve during SAMe therapy. DISCUSSION Molecular mechanisms proposed for LND neuropathology include GTP depletion in the brain leading to impaired dopamine synthesis, dysfunction of G-protein-mediated signal transduction, and defective developmental programming of dopamine neurons. The improvement of our LND patients on SAMe, particularly the hallmark self-injurious behaviour, echoed clinical progress reported with another purine nucleotide depletion disorder, Arts Syndrome, but contrasted lack of benefit with the purine disorder adenylosuccinate lyase deficiency. This first report of a trial of SAMe therapy in LND children showed remarkably encouraging results that warrant larger studies.

Utility of AVP gene testing in familial neurohypophyseal diabetes insipidus

Context  Familial neurohypophyseal diabetes insipidus (FNDI) is a rare disorder resulting from arginine vasopressin (AVP) gene mutations. A partial defect in AVP secretion occurs early in the course of FNDI and may not be detected by a water deprivation test (WDT). Testing for AVP gene mutations may confirm a diagnosis of FNDI when a WDT is inconclusive and may also predict individuals who will later develop FNDI.

Is it time to commence newborn screening for congenital adrenal hyperplasia in Australia

21‐Hydroxylase deficiency (21‐OHD) is the most common cause of congenital adrenal hyperplasia, with an incidence of 1 : 14 000 live births and equal prevalence among males and females. Newborns with the most severe “salt‐wasting” form of 21‐OHD are susceptible to salt‐wasting crises in the first few weeks of life. This is associated with morbidity and mortality. 21‐OHD newborn screening (NBS) is currently performed in many countries. Despite several prominent medical societies recommending 21‐OHD NBS, no state in Australia currently screens for this condition. We report a case that illustrates the need to reconsider including 21‐OHD in NBS. 21‐OHD NBS can be reliable, sensitive and effective in reducing morbidity and mortality.

Maternal gonadal mosaicism causing ornithine transcarbamylase deficiency.

Ornithine transcarbamylase (OTC) deficiency (McKusick 311250), an X-linked inherited disorder, often presents in males with severe neonatal onset of hyperammonemia. Maternal gonadal mosaicism in OTC deficiency was postulated previously, but no cases have been reported. We report on a family in which two consecutive males were affected with OTC deficiency, which was proven biochemically with characteristic metabolites and absent enzyme activity in liver. OTC genotyping in both brothers showed a new mutation in exon 6 (Met206Arg: ATG-->AGG), which encodes part of the equatorial H6 alpha-helix. Biochemical investigations confirmed normal results in the mother and grandmother and the absence of OTC activity in the affected males. Genotyping of the mother and grandmother was performed on peripheral blood leukocytes and skin fibroblasts and showed no mutation in the somatic cells. The recurrence of OTC deficiency in offsprings of a woman with normal genotype strongly suggests gonadal mosaicism. Gonadal mosaicism needs to be considered when counseling couples in which the mother has had a previously affected child with OTC deficiency but apparently is not a carrier.

21-Hydroxylase Genotyping in Australasian Patients with Congenital Adrenal Hyperplasia

Mutations in CYP21 (21-hydroxylase) lead to congenital adrenal hyperplasia (CAH). We genotyped 26 probands with CAH by PCR-sequencing the entire CYP21 gene. 25/26 had homozygous or compound heterozygous mutations. The frequencies of mutations were similar to other populations with deletion/hybrid, I2 G splice and I172N the most common. Five patients with a I172N allele predicting simple-virilising CAH had a salt-wasting phenotype. Two other probands also had a more severe phenotype than predicted by genotype. Two families had both non-classic and salt-wasting phenotypes arising from combinations of three deleterious alleles. Two novel CYP21 alleles were detected: D106N and a large deletion encompassing CYP21 and adjacent pseudogene. Two rare CYP21 alleles were also found. Three of these four novel/rare alleles were only detected as a result of sequencing the entire CYP21 gene. Entire CYP21 sequencing will increase the number of mutations detected in CAH, and in combination with functional studies should contribute a greater understanding of phenotype-genotype correlations.

Androgen receptor genotyping in a large Australasian cohort with androgen insensitivity syndrome; identification of four novel mutations.

We genotyped the androgen receptor (AR) gene in 31 Australasian patients with androgen insensitivity syndrome (AIS). The entire coding region of AR was examined including analysis of polymorphic CAG and GGN repeats in all patients. AR defects were found in 66.7% (6/9) of patients with complete AIS (CAIS) and 13.6% (3/22) of patients with partial AIS (PAIS). A novel deletion (N858delG) leading to a premature stop codon was found in CAIS patient P1. CAIS patient P2 has a novel deletion (N2676delGAGT) resulting in a stop at codon 787. These mutations would result in inactivation of AR protein. A novel insertion of a cysteine residue in the first zinc finger of the AR DNA-binding domain (N2045_2047dupCTG) was found in CAIS patient P3. PAIS patient P4 has a novel amino acid substitution (Arg760Ser) in the AR ligand binding domain, which may impair ligand binding. Five patients were found to have previously reported AR mutations and no mutations were identified in the remaining patients.

Early diagnosis of adenylosuccinate lyase deficiency using a high-throughput screening method and a trial of oral S-adenosyl-L-methionine as a treatment method

The aim of this study was to develop a high‐throughput urine screening technique for adenylosuccinate lyase (ADSL) deficiency and to evaluate S‐adenosyl‐l‐methionine (SAMe) as a potential treatment for this disorder.