Extremely high mutation load of the mitochondrial 8993 T>G mutation in a newborn: implications for prognosis and family planning decisions.

UNLABELLED: The propositus presented with hypotonia, respiratory failure, and seizures in the newborn period and was found to have severe hyperlactacidemia and a hypertrophic heart. He carried a de novo pathogenic mutation (m.8993 T>G) in the gene encoding subunit 6 of the mitochondrial ATP synthase (MTATP6). Although the lactate concentration in serum normalized and the proband recovered after a short period at the neonatal intensive care unit, his ultimate motor and cognitive development was poor. Brain MRI at the age of 6 months showed bilaterally signal abnormalities in the caudate nucleus, putamen, thalamus, and mesencephalon. He died at the age of 9 months. The difficulty in genetic counseling in families with a maternal mitochondrial mutation disorder is emphasized. CONCLUSION: Here, we report on a neonate with the m.8993 T>G mutation and emphasize implications of mtDNA disorders on family planning decisions.

Lactic acidosis in a newborn with adrenal calcifications.

A patient is reported who presented in the newborn period with an unusual combination of congenital lactic acidosis and bilateral calcifications in the adrenal medulla, visible on standard abdominal x-ray and ultrasound examination. At birth, the proband was hypotonic and dystrophic. She developed respiratory insufficiency, cardiomegaly, and hepatomegaly and died at the age of 38 d. Examination of postmortem heart muscle revealed multiple areas of myocardial infarction with dystrophic calcifications. In the medulla of the adrenal glands, foci of necrosis and calcifications, and in the liver, multiple zones of necrosis and iron deposition were detected. Biochemical analysis in heart muscle revealed a decreased activity of complex IV of the oxidative phosphorylation (OXPHOS) and in liver a combined deficiency involving the complexes I, III, IV, and V. The findings were suggestive of a defect in biosynthesis of the mitochondrially encoded subunits of the OXPHOS complexes. Extensive analysis of the proband's mitochondrial DNA revealed neither pathogenic deletions and point mutations nor copy number alterations. Relative amounts of mitochondrial transcripts for the ribosomal mitochondrial 12S rRNA (12S) and mitochondrial 16S rRNA (16S) were significantly increased suggesting a compensatory mechanism involving the transcription machinery to low levels of translation. The underlying molecular defect has not been identified yet.

Unilateral bloody nipple discharge in a two-month-old male.

Bloody nipple discharge is a rare but distressing finding in neonates and infants. We report on a 2-month-old boy with unilateral bloody nipple discharge. Ultrasound examination revealed dilated mammary ducts. This benign phenomenon is most likely to be caused by mammary ductal ectasia. Invasive investigations or surgery should be avoided in neonates or infants with bloody nipple discharge unless the discharge is unilateral, spontaneous, persistent and accompanied with a palpable mass. Otherwise only serial clinical follow-up is recommended until spontaneous resolution.

Clinical and molecular phenotype of Aicardi-Goutieres syndrome.

Aicardi-Goutieres syndrome (AGS) is a genetic encephalopathy whose clinical features mimic those of acquired in utero viral infection. AGS exhibits locus heterogeneity, with mutations identified in genes encoding the 3'-->5' exonuclease TREX1 and the three subunits of the RNASEH2 endonuclease complex. To define the molecular spectrum of AGS, we performed mutation screening in patients, from 127 pedigrees, with a clinical diagnosis of the disease. Biallelic mutations in TREX1, RNASEH2A, RNASEH2B, and RNASEH2C were observed in 31, 3, 47, and 18 families, respectively. In five families, we identified an RNASEH2A or RNASEH2B mutation on one allele only. In one child, the disease occurred because of a de novo heterozygous TREX1 mutation. In 22 families, no mutations were found. Null mutations were common in TREX1, although a specific missense mutation was observed frequently in patients from northern Europe. Almost all mutations in RNASEH2A, RNASEH2B, and RNASEH2C were missense. We identified an RNASEH2C founder mutation in 13 Pakistani families. We also collected clinical data from 123 mutation-positive patients. Two clinical presentations could be delineated: an early-onset neonatal form, highly reminiscent of congenital infection seen particularly with TREX1 mutations, and a later-onset presentation, sometimes occurring after several months of normal development and occasionally associated with remarkably preserved neurological function, most frequently due to RNASEH2B mutations. Mortality was correlated with genotype; 34.3% of patients with TREX1, RNASEH2A, and RNASEH2C mutations versus 8.0% RNASEH2B mutation-positive patients were known to have died (P=.001). Our analysis defines the phenotypic spectrum of AGS and suggests a coherent mutation-screening strategy in this heterogeneous disorder. Additionally, our data indicate that at least one further AGS-causing gene remains to be identified.

Congenital pontocerebellar atrophy and telencephalic defects in three siblings: a new subtype.

We report three siblings, two of whom had a neuropathological study, with a new subtype of congenital ponto-cerebellar atrophy (PCH). In addition to the brain stem and cerebellar anomalies common to all types of this heterogeneous condition, there were unique developmental defects in the telencephalon: absence of the claustrum, diffuse cortical changes particularly in the insula and an extremely small brain. In an attempt to shed some light on the pathogenesis of this developmental disorder, we have analyzed the pattern of brain stem and cerebellar abnormalities in ours and in previously reported patients with PCH, to possibly distinguish primary from secondary effects of the mutant gene upon the cerebellar circuitry, and compared our patients' cerebellar and cerebral defects to those of some other human brain malformations and to mutant mice with both hindbrain and forebrain anomalies. Although this and previous observations of familial congenital PCH with apparent autosomal recessive inheritance spawn the endeavor to compare and classify patients into subgroups, any final classification must await identification and molecular characterization of the causal gene(s).

Phototherapy-mediated syndrome of inappropriate secretion of antidiuretic hormone in an in utero selective serotonin reuptake inhibitor-exposed newborn infant.

Although selective serotonin reuptake inhibitors (SSRIs) have gained wide acceptance in the off-label treatment of mental disorders in pregnant women, there seems to be an increased risk for serotonergic adverse effects in newborn infants who are exposed to SSRIs during late pregnancy. Hyponatremia as a result of the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is a relatively common serious side effect of the use of SSRIs in (mostly elderly) adults. Severe hyponatremia as a result of an SIADH is proposed here as part of a neonatal serotonin toxicity syndrome in a newborn infant who was exposed prenatally to an SSRI. The definite reversal to normal serum sodium levels after fluid restriction, the lack of any alternative cause for the SIADH, and the positive temporal relation with a high score on a widely used adverse drug reaction probability scale offer solid support for the hypothesis of a causal relationship between the SIADH and the prenatal sertraline exposure in our neonate. Moreover, accumulative data on the acute enhancement of serotonergic transmission by intense illumination led us to hypothesize that phototherapy used to treat hyperbilirubinemia in the newborn infant could have been the ultimate environmental trigger for this proposed new cause of iatrogenic neonatal SIADH. The speculative role of phototherapy as a physical trigger for this drug-related adverse event should be confirmed in other cases by thorough study of the serotonin metabolism, assay of SSRI levels in cord blood, and serial measurement of plasma levels in exposed neonates. As phototherapy is used frequently in jaundiced neonates and an apparently increasing number of infants are born to mothers who take SSRIs, serotonin toxicity in neonates deserves increased attention.

Transplacental passage of a nonionic contrast agent.

UNLABELLED: We report the presence of iopromide in the bowel and urine of a preterm infant, born 10 days after intravenous administration of the nonionic monomer to his mother. Excessive urinary iodine excretion and borderline hyperthyrotropinaemia were observed in the infant. Moreover, crossing of the fetal blood-brain barrier was demonstrated by detection of the angiographic material in CSF and thus direct fetal neurotoxic effects cannot be excluded. CONCLUSION: These widely used contrast media may cross the placenta and accumulate in various fetal tissues in significant amounts causing possible neonatal toxicity. Therefore the perinatal safety of these diagnostic agents should at least be questioned.

Processing of N-linked carbohydrate chains in a patient with glucosidase I deficiency (CDG type IIb).

Recently, we reported a novel congenital disorder of glycosylation (CDG-IIb) caused by severe deficiency of the glucosidase I. The enzyme cleaves the alpha1,2-glucose residue from the asparagine-linked Glc(3)-Man(9)-GlcNAc(2) precursor, which is crucial for oligosaccharide maturation. The patient suffering from this disease was compound-heterozygous for two mutations in the glucosidase I gene, a T-->C transition in the paternal allele and a G-->C transition in the maternal allele. This gives rise in the glucosidase I polypeptide to the substitution of Arg486 by Thr and Phe652 by Leu, respectively. Kinetic studies using detergent extracts from cultured fibroblasts showed that the glucosidase I activity in the patient's cells was < 1% of the control level, with intermediate values in the parental cells. No significant differences in the activities of other processing enzymes, including oligosaccharyltransferase, glucosidase II, and Man(9)-mannosidase, were observed. By contrast, the patient's fibroblasts displayed a two- to threefold higher endo-alpha1,2-mannosidase activity, associated with an increased level of enzyme-specific mRNA-transcripts. This points to the lack of glucosidase I activity being compensated for, to some extent, by increase in the activity of the pathway involving endo-alpha1,2-mannosidase; this would also explain the marked urinary excretion of Glc(3)-Man. Comparative analysis of [(3)H]mannose-labeled N-glycoproteins showed that, despite the dramatically reduced glucosidase I activity, the bulk of the N-linked carbohydrate chains (>80%) in the patient's fibroblasts appeared to have been processed correctly, with only approximately 16% of the N-glycans being arrested at the Glc(3)-Man(9-7)-GlcNAc(2) stage. These structural and enzymatic data provide a reasonable basis for the observation that the sialotransferrin pattern, which frequently depends on the type of glycosylation disorder, appears to be normal in the patient. The human glucosidase I gene contains four exons separated by three introns with exon-4 encoding for the large 64-kDa catalytic domain of the enzyme. The two base mutations giving rise to substitution of Arg486 by Thr and Phe652 by Leu both reside in exon-4, consistent with their deleterious effect on enzyme activity. Incorporation of either mutation into wild-type glucosidase I resulted in the overexpression of enzyme mutants in COS 1 cells displaying no measurable catalytic activity. The Phe652Leu but not the Arg486Thr protein mutant showed a weak binding to a glucosidase I-specific affinity resin, indicating that the two amino acids affect polypeptide folding and active site formation differently.