Motor Responses in Pediatric Pompe Disease in the ADVANCE Participant Cohort

Background: ADVANCE (NCT01526785) presented an opportunity to obtain a more nuanced understanding of motor function changes in treatment-experienced children with Pompe disease receiving 4000L-production-scale alglucosidase alfa for 52 weeks. Objective: To estimate minimal detectable change (MDC) and effect size on Gross Motor Function Measure-88 (GMFM-88) after 52 weeks of 4000L alglucosidase alfa (complete data N =  90). Methods: The GMFM-88 mean total % score changes, MDC, and effect size were analyzed post hoc by Pompe Motor Function Level at enrollment, age groups at enrollment, and fraction of life on pre-study 160L-production-scale alglucosidase alfa. Results: Overall, participants aged <  2 years surpassed MDC at Week 52 (change [mean±standard deviation] 21.1±14.1, MDC range 5.7–13.3, effect size 1.1), whereas participants aged≥2 years did not attain this (change –0.9±15.3, MDC range 10.8–25.2, effect size –0.03). In participants aged <  2 years, improvements surpassed the MDC for walkers (change 17.1±13.3, MDC range 3.0–6.9, effect size 1.7), supported standers (change 35.2±18.0, MDC range 5.9–13.7, effect size 1.8) and sitters (change 24.1±12.1, MDC range 2.6–6.2, effect size 2.7). Age-independent MDC ranges were only attained by walkers (change 7.7±12.3, MDC range 6.4–15.0, effect size 0.4) and sitters (change 9.9±17.2, MDC range 3.3–7.7, effect size 0.9). Conclusions: These first GMFM-88 minimal-detectable-change estimates for alglucosidase alfa-treated Pompe disease offer utility for monitoring motor skills. Trial registration: ClinicalTrials.gov; NCT01526785; Registered 6 February 2012; https://clinicaltrials.gov/ct2/show/NCT01526785

Management of COVID-19 infection in organic acidemias

The COVID-19 pandemic has affected the health and healthcare of individuals of all ages worldwide. There have been multiple reports and reviews documenting a milder effect and decreased morbidity and mortality in the pediatric population, but there have only been a small number of reports discussing the SARS-CoV-2 infection in the setting of an inborn error of metabolism (IEM). Here, we report two patients with underlying metabolic disorders, propionic acidemia and glutaric aciduria type 1, and discuss their clinical presentation, as well as their infectious and metabolic management. Our report demonstrates that individuals with an underlying IEM are at risk of metabolic decompensation in the setting of a COVID-19 infection. The SARS-CoV-2 virus does not appear to cause a more severe metabolic deterioration than is typical.

Biallelic Variants in LAMB1 Causing Hydranencephaly: A Severe Phenotype of a Rare Malformative Encephalopathy

Case Report  A 32-year-old female with a history of three prior pregnancy losses presented for genetic testing following an ultrasonography diagnosis of fetal hydranencephaly. Baby was born via C-section and was noted to have a head circumference of 48 cm, in addition to ocular and cardiac anomalies and dysmorphic features. Whole genome sequencing revealed a homozygous variant in LAMB1 gene. Discussion  The pathobiogenesis of hydranencephaly is incompletely understood and is attributed to vascular, infectious, or genetic etiology. Herein we present LAMB1 as a monogenic cause of fetal hydranencephaly which was incompatible with life. Previously, LAMB1 -associated phenotype consisted of cobblestone lissencephaly and hydrocephalus, developmental delay, and seizures. Our proband expands the phenotypic spectrum of this malformative encephalopathy.

Respiratory function during enzyme replacement therapy in late-onset Pompe disease: longitudinal course, prognostic factors, and the impact of time from diagnosis to treatment start

OBJECTIVE

To examine respiratory muscle function among late-onset Pompe disease (LOPD) patients in the Pompe Registry (NCT00231400/Sanofi Genzyme) during enzyme replacement therapy (ERT) with alglucosidase alfa by assessing the longitudinal course of forced vital capacity (FVC), prognostic factors for FVC, and impact of time from diagnosis to ERT initiation.

METHODS

Longitudinal FVC data from LOPD (symptom onset > 12 months or ≤ 12 months without cardiomyopathy) patients were analyzed. Patients had to have baseline FVC (percent predicted upright) assessments at ERT start and ≥ 2 valid post-baseline assessments. Longitudinal analyses used linear mixed-regression models.

RESULTS

Among 396 eligible patients, median baseline FVC was 66.9% (range 9.3-126.0). FVC remained stable during the 5-year follow-up (slope = - 0.17%, p = 0.21). Baseline FVC was lower among various subgroups, including patients who were male; older at ERT initiation; had a longer duration from symptom onset to ERT initiation; and had more advanced disease at baseline (based on respiratory support use, inability to ambulate, ambulation device use). Age at symptom onset was not associated with baseline degree of respiratory dysfunction. Differences between subgroups observed at baseline remained during follow-up. Shorter time from diagnosis to ERT initiation was associated with higher FVC after 5 years in all patients and the above subgroups using a cut-off of 1.7 years.

CONCLUSION

FVC stability over 5 years suggests that respiratory function is preserved during long-term ERT in real-world settings. Early initiation of alglucosidase alfa was associated with preservation of FVC in LOPD patients with better respiratory function at the time of treatment initiation.

Clinical spectrum of individuals with pathogenic NF1 missense variants affecting p.Met1149, p.Arg1276, and p.Lys1423: genotype-phenotype study in neurofibromatosis type 1

We report 281 individuals carrying a pathogenic recurrent NF1 missense variant at p.Met1149, p.Arg1276, or p.Lys1423, representing three nontruncating NF1 hotspots in the University of Alabama at Birmingham (UAB) cohort, together identified in 1.8% of unrelated NF1 individuals. About 25% (95% confidence interval: 20.5-31.2%) of individuals heterozygous for a pathogenic NF1 p.Met1149, p.Arg1276, or p.Lys1423 missense variant had a Noonan-like phenotype, which is significantly more compared with the "classic" NF1-affected cohorts (all p < .0001). Furthermore, p.Arg1276 and p.Lys1423 pathogenic missense variants were associated with a high prevalence of cardiovascular abnormalities, including pulmonic stenosis (all p < .0001), while p.Arg1276 variants had a high prevalence of symptomatic spinal neurofibromas (p < .0001) compared with "classic" NF1-affected cohorts. However, p.Met1149-positive individuals had a mild phenotype, characterized mainly by pigmentary manifestations without externally visible plexiform neurofibromas, symptomatic spinal neurofibromas or symptomatic optic pathway gliomas. As up to 0.4% of unrelated individuals in the UAB cohort carries a p.Met1149 missense variant, this finding will contribute to more accurate stratification of a significant number of NF1 individuals. Although clinically relevant genotype-phenotype correlations are rare in NF1, each affecting only a small percentage of individuals, together they impact counseling and management of a significant number of the NF1 population.

Clinical characteristics and genotypes in the ADVANCE baseline data set, a comprehensive cohort of US children and adolescents with Pompe disease

PURPOSE

To characterize clinical characteristics and genotypes of patients in the ADVANCE study of 4000 L-scale alglucosidase alfa (NCT01526785), the largest prospective United States Pompe disease cohort to date.

METHODS

Patients aged ≥1 year with confirmed Pompe disease previously receiving 160 L alglucosidase alfa were eligible. GAA genotypes were determined before/at enrollment. Baseline assessments included histories/physical exams, Gross Motor Function Measure-88 (GMFM-88), pulmonary function tests, and cardiac assessments.

RESULTS

Of 113 enrollees (60 male/53 female) aged 1-18 years, 87 had infantile-onset Pompe disease (IOPD) and 26 late-onset (LOPD). One hundred eight enrollees with GAA genotypes had 215 pathogenic variants (220 including combinations): 118 missense (4 combinations), 23 splice, 35 nonsense, 34 insertions/deletions, 9 duplications (1 combination), 6 other; c.2560C>T (n = 23), c.-32-13T>G (n = 13), and c.525delT (n = 12) were most common. Four patients had previously unpublished variants, and 14/83 (17%) genotyped IOPD patients were cross-reactive immunological material-negative. All IOPD and 6/26 LOPD patients had cardiac involvement, all without c.-32-13T>G. Thirty-two (26 IOPD, 6 LOPD) were invasively ventilated. GMFM-88 total %scores (mean ± SD, median, range): overall 46.3 ± 33.0% (47.9%, 0.0-100.0%), IOPD 41.6 ± 31.64% (38.9%, 0.0-99.7%), LOPD: 61.8 ± 33.2 (70.9%, 0.0-100.0%).

CONCLUSION

ADVANCE, a uniformly assessed cohort comprising most US children and adolescents with treated Pompe disease, expands understanding of the phenotype and observed variants in the United States.

Can Functional Polymorphisms in VEGF and MMP Predict Intraventricular Hemorrhage in Extremely Preterm Newborns?

BACKGROUND

The pathophysiology of intraventricular hemorrhage (IVH) is multifactorial. This study attempts to identify genetic and clinical factors contributing to IVH in newborns with a focus on those born ≤28 weeks of gestation.

METHODS

This was a prospective study of 382 consecutive newborns admitted to the neonatal intensive care unit. DNA purification was conducted using standard methods. TaqMan SNP assays were conducted for functional polymorphisms in VEGF (RS699947, RS2010963, RS3025039, and RS1570360) and MMP2 (RS243685 and RS2285053) genes. An RFLP assay was done for a polymorphism in MMP9 (RS3918242).

RESULTS

The GG genotype in VEGF RS1570360 (p = 0.013) and the CC genotype in VEGF RS699947 (p = 0.036) were associated with a lower incidence of IVH amongst newborns ≤28 weeks of gestation. Chorioamnionitis, Caucasian race, and patent ductus arteriosus were associated with a higher incidence of IVH. A binary logistic regression analysis of clinical and SNP data that was significant from bivariate analysis demonstrated that VEGF RS1570360 was significantly associated with IVH (p = 0.017).

CONCLUSION

This study demonstrated that the GA/AA genotype in VEGF RS1570360 and the AA/AC genotype in VEGF RS699947 were associated with higher incidence rates of IVH in newborns ≤28 weeks of gestation. A future study is warranted to comprehensively examine VEGF polymorphisms in association with IVH.

Genotype-Phenotype Correlation in NF1: Evidence for a More Severe Phenotype Associated with Missense Mutations Affecting NF1 Codons 844-848

Neurofibromatosis type 1 (NF1), a common genetic disorder with a birth incidence of 1:2,000-3,000, is characterized by a highly variable clinical presentation. To date, only two clinically relevant intragenic genotype-phenotype correlations have been reported for NF1 missense mutations affecting p.Arg1809 and a single amino acid deletion p.Met922del. Both variants predispose to a distinct mild NF1 phenotype with neither externally visible cutaneous/plexiform neurofibromas nor other tumors. Here, we report 162 individuals (129 unrelated probands and 33 affected relatives) heterozygous for a constitutional missense mutation affecting one of five neighboring NF1 codons-Leu844, Cys845, Ala846, Leu847, and Gly848-located in the cysteine-serine-rich domain (CSRD). Collectively, these recurrent missense mutations affect ∼0.8% of unrelated NF1 mutation-positive probands in the University of Alabama at Birmingham (UAB) cohort. Major superficial plexiform neurofibromas and symptomatic spinal neurofibromas were more prevalent in these individuals compared with classic NF1-affected cohorts (both p < 0.0001). Nearly half of the individuals had symptomatic or asymptomatic optic pathway gliomas and/or skeletal abnormalities. Additionally, variants in this region seem to confer a high predisposition to develop malignancies compared with the general NF1-affected population (p = 0.0061). Our results demonstrate that these NF1 missense mutations, although located outside the GAP-related domain, may be an important risk factor for a severe presentation. A genotype-phenotype correlation at the NF1 region 844-848 exists and will be valuable in the management and genetic counseling of a significant number of individuals.

Durable and sustained immune tolerance to ERT in Pompe disease with entrenched immune responses

BACKGROUND

Enzyme replacement therapy (ERT) has prolonged survival and improved clinical outcomes in patients with infantile Pompe disease (IPD), a rapidly progressive neuromuscular disorder. Yet marked interindividual variability in response to ERT, primarily attributable to the development of antibodies to ERT, remains an ongoing challenge. Immune tolerance to ongoing ERT has yet to be described in the setting of an entrenched immune response.

METHODS

Three infantile Pompe patients who developed high and sustained rhGAA IgG antibody titers (HSAT) and received a bortezomib-based immune tolerance induction (ITI) regimen were included in the study and were followed longitudinally to monitor the long-term safety and efficacy. A trial to taper the ITI protocol was attempted to monitor if true immune tolerance was achieved.

RESULTS

Bortezomib-based ITI protocol was safely tolerated and led to a significant decline in rhGAA antibody titers with concomitant sustained clinical improvement. Two of the 3 IPD patients were successfully weaned off all ITI protocol medications and continue to maintain low/no antibody titers. ITI protocol was significantly tapered in the third IPD patient. B cell recovery was observed in all 3 IPD patients.

CONCLUSION

This is the first report to our knowledge on successful induction of long-term immune tolerance in patients with IPD and HSAT refractory to agents such as cyclophosphamide, rituximab, and methotrexate, based on an approach using the proteasome inhibitor bortezomib. As immune responses limit the efficacy and cost-effectiveness of therapy for many conditions, proteasome inhibitors may have new therapeutic applications.

FUNDING

This research was supported by a grant from the Genzyme Corporation, a Sanofi Company (Cambridge, Massachusetts, USA), and in part by the Lysosomal Disease Network, a part of NIH Rare Diseases Clinical Research Network (RDCRN).

Premature pubarche in children with Pompe disease

Pompe disease (PD), or glycogen storage disease type II, results from deficiency of acid α-glucosidase. Patients with infantile-onset PD die by early childhood if untreated. Patient survival has improved with enzyme replacement therapy. We report a case series of 8 patients with infantile-onset PD on enzyme replacement therapy with premature pubarche.

Methylmalonic acidemia presenting as persistent pulmonary hypertension of the newborn

Persistent pulmonary hypertension of the newborn (PPHN) results from disruption of the normal fetal-neonatal circulatory transition and may be associated with meconium aspiration, group B streptococcal sepsis, pneumonia, respiratory distress syndrome, congenital diaphragmatic hernia and pulmonary hypoplasia. Seventeen percent of cases are considered idiopathic since there is no identifiable cause. Although it is recognized that acidosis and hypoxia from any cause in neonates may produce pulmonary vasoconstriction and maintain pulmonary hypertension, PPHN has not been reported in inborn errors of metabolism (IEM) associated with metabolic acidosis like methyl malonic acidemia (MMA). We report the first case in the literature of MMA presenting concomitantly with PPHN. Undiagnosed IEMs, like MMA, could represent a subset of idiopathic cases of PPHN. Infants and neonates have a limited repertoire with which to respond to an overwhelming illness. Because metabolic diseases are rare, they are considered only after excluding more common causes of neonatal distress. PPHN is therefore more likely to be attributed to meconium aspiration, sepsis, pneumonia or respiratory distress syndrome than to an IEM. The advent of expanded newborn screening has made pre-symptomatic diagnosis of several IEMs including MMA possible. However, not all IEMs are identified, and in some instances, an infant who has an IEM may become ill before the results of the newborn screen become available. Early diagnosis of IEM is crucial to prevent catastrophic consequences and the awareness of an association with PPHN would lead to an aggressive search of an underlying IEM and its management.

Novel frem1-related mouse phenotypes and evidence of genetic interactions with gata4 and slit3

The FRAS1-related extracellular matrix 1 (FREM1) gene encodes an extracellular matrix protein that plays a critical role in the development of multiple organ systems. In humans, recessive mutations in FREM1 cause eye defects, congenital diaphragmatic hernia, renal anomalies and anorectal malformations including anteriorly placed anus. A similar constellation of findings-microphthalmia, cryptophthalmos, congenital diaphragmatic hernia, renal agenesis and rectal prolapse-have been described in FREM1-deficient mice. In this paper, we identify a homozygous Frem1 missense mutation (c.1687A>T, p.Ile563Phe) in an N-ethyl-N-nitrosourea (ENU)-derived mouse strain, crf11, with microphthalmia, cryptophthalmos, renal agenesis and rectal prolapse. This mutation affects a highly conserved residue in FREM1's third CSPG domain. The p.Ile563Phe change is predicted to be deleterious and to cause decreased FREM1 protein stability. The crf11 allele also fails to complement the previously described eyes2 allele of Frem1 (p.Lys826*) providing further evidence that the crf11 phenotype is due to changes affecting Frem1 function. We then use mice bearing the crf11 and eyes2 alleles to identify lung lobulation defects and decreased anogenital distance in males as novel phenotypes associated with FREM1 deficiency in mice. Due to phenotypic overlaps between FREM1-deficient mice and mice that are deficient for the retinoic acid-responsive transcription factor GATA4 and the extracellular matrix protein SLIT3, we also perform experiments to look for in vivo genetic interactions between the genes that encode these proteins. These experiments reveal that Frem1 interacts genetically with Gata4 in the development of lung lobulation defects and with Slit3 in the development of renal agenesis. These results demonstrate that FREM1-deficient mice faithfully recapitulate many of the phenotypes seen in individuals with FREM1 deficiency and that variations in GATA4 and SLIT3 expression modulate some FREM1-related phenotypes in mice.

An allelic series of mice reveals a role for RERE in the development of multiple organs affected in chromosome 1p36 deletions

Individuals with terminal and interstitial deletions of chromosome 1p36 have a spectrum of defects that includes eye anomalies, postnatal growth deficiency, structural brain anomalies, seizures, cognitive impairment, delayed motor development, behavior problems, hearing loss, cardiovascular malformations, cardiomyopathy, and renal anomalies. The proximal 1p36 genes that contribute to these defects have not been clearly delineated. The arginine-glutamic acid dipeptide (RE) repeats gene (RERE) is located in this region and encodes a nuclear receptor coregulator that plays a critical role in embryonic development as a positive regulator of retinoic acid signaling. Rere-null mice die of cardiac failure between E9.5 and E11.5. This limits their usefulness in studying the role of RERE in the latter stages of development and into adulthood. To overcome this limitation, we created an allelic series of RERE-deficient mice using an Rere-null allele, om, and a novel hypomorphic Rere allele, eyes3 (c.578T>C, p.Val193Ala), which we identified in an N-ethyl-N-nitrosourea (ENU)-based screen for autosomal recessive phenotypes. Analyses of these mice revealed microphthalmia, postnatal growth deficiency, brain hypoplasia, decreased numbers of neuronal nuclear antigen (NeuN)-positive hippocampal neurons, hearing loss, cardiovascular malformations–aortic arch anomalies, double outlet right ventricle, and transposition of the great arteries, and perimembranous ventricular septal defects–spontaneous development of cardiac fibrosis and renal agenesis. These findings suggest that RERE plays a critical role in the development and function of multiple organs including the eye, brain, inner ear, heart and kidney. It follows that haploinsufficiency of RERE may contribute–alone or in conjunction with other genetic, environmental, or stochastic factors–to the development of many of the phenotypes seen in individuals with terminal and interstitial deletions that include the proximal region of chromosome 1p36.

Deficiency of FRAS1-related extracellular matrix 1 (FREM1) causes congenital diaphragmatic hernia in humans and mice

Congenital diaphragmatic hernia (CDH) is a common life-threatening birth defect. Recessive mutations in the FRAS1-related extracellular matrix 1 (FREM1) gene have been shown to cause bifid nose with or without anorectal and renal anomalies (BNAR) syndrome and Manitoba oculotrichoanal (MOTA) syndrome, but have not been previously implicated in the development of CDH. We have identified a female child with an isolated left-sided posterolateral CDH covered by a membranous sac who had no features suggestive of BNAR or MOTA syndromes. This child carries a maternally-inherited ~86 kb FREM1 deletion that affects the expression of FREM1's full-length transcripts and a paternally-inherited splice site mutation that causes activation of a cryptic splice site, leading to a shift in the reading frame and premature termination of all forms of the FREM1 protein. This suggests that recessive FREM1 mutations can cause isolated CDH in humans. Further evidence for the role of FREM1 in the development of CDH comes from an N-ethyl-N-nitrosourea -derived mouse strain, eyes2, which has a homozygous truncating mutation in Frem1. Frem1(eyes2) mice have eye defects, renal agenesis and develop retrosternal diaphragmatic hernias which are covered by a membranous sac. We confirmed that Frem1 is expressed in the anterior portion of the developing diaphragm and found that Frem1(eyes2) embryos had decreased levels of cell proliferation in their developing diaphragms when compared to wild-type embryos. We conclude that FREM1 plays a critical role in the development of the diaphragm and that FREM1 deficiency can cause CDH in both humans and mice.

Phenotypic heterogeneity of genomic disorders and rare copy-number variants

BACKGROUND

Some copy-number variants are associated with genomic disorders with extreme phenotypic heterogeneity. The cause of this variation is unknown, which presents challenges in genetic diagnosis, counseling, and management.

METHODS

We analyzed the genomes of 2312 children known to carry a copy-number variant associated with intellectual disability and congenital abnormalities, using array comparative genomic hybridization.

RESULTS

Among the affected children, 10.1% carried a second large copy-number variant in addition to the primary genetic lesion. We identified seven genomic disorders, each defined by a specific copy-number variant, in which the affected children were more likely to carry multiple copy-number variants than were controls. We found that syndromic disorders could be distinguished from those with extreme phenotypic heterogeneity on the basis of the total number of copy-number variants and whether the variants are inherited or de novo. Children who carried two large copy-number variants of unknown clinical significance were eight times as likely to have developmental delay as were controls (odds ratio, 8.16; 95% confidence interval, 5.33 to 13.07; P=2.11×10(-38)). Among affected children, inherited copy-number variants tended to co-occur with a second-site large copy-number variant (Spearman correlation coefficient, 0.66; P<0.001). Boys were more likely than girls to have disorders of phenotypic heterogeneity (P<0.001), and mothers were more likely than fathers to transmit second-site copy-number variants to their offspring (P=0.02).

CONCLUSIONS

Multiple, large copy-number variants, including those of unknown pathogenic significance, compound to result in a severe clinical presentation, and secondary copy-number variants are preferentially transmitted from maternal carriers. (Funded by the Simons Foundation Autism Research Initiative and the National Institutes of Health.).

Update of PAX2 mutations in renal coloboma syndrome and establishment of a locus-specific database

Renal coloboma syndrome, also known as papillorenal syndrome is an autosomal-dominant disorder characterized by ocular and renal malformations. Mutations in the paired-box gene, PAX2, have been identified in approximately half of individuals with classic findings of renal hypoplasia/dysplasia and abnormalities of the optic nerve. Prior to 2011, there was no actively maintained locus-specific database (LSDB) cataloguing the extent of genetic variation in the PAX2 gene and phenotypic variation in individuals with renal coloboma syndrome. Review of published cases and the collective diagnostic experience of three laboratories in the United States, France, and New Zealand identified 55 unique mutations in 173 individuals from 86 families. The three clinical laboratories participating in this collaboration contributed 28 novel variations in 68 individuals in 33 families, which represent a 50% increase in the number of variations, patients, and families published in the medical literature. An LSDB was created using the Leiden Open Variation Database platform: www.lovd.nl/PAX2. The most common findings reported in this series were abnormal renal structure or function (92% of individuals), ophthalmological abnormalities (77% of individuals), and hearing loss (7% of individuals). Additional clinical findings and genetic counseling implications are discussed.

Microdeletion 9q22.3 syndrome includes metopic craniosynostosis, hydrocephalus, macrosomia, and developmental delay

Basal cell nevus syndrome (BCNS), also known as Gorlin syndrome (OMIM #109400) is a well-described rare autosomal dominant condition due to haploinsufficiency of PTCH1. With the availability of comparative genomic hybridization arrays, increasing numbers of individuals with microdeletions involving this locus are being identified. We present 10 previously unreported individuals with 9q22.3 deletions that include PTCH1. While 7 of the 10 patients (7 females, 3 males) did not meet strict clinical criteria for BCNS at the time of molecular diagnosis, almost all of the patients were too young to exhibit many of the diagnostic features. A number of the patients exhibited metopic craniosynostosis, severe obstructive hydrocephalus, and macrosomia, which are not typically observed in BCNS. All individuals older than a few months of age also had developmental delays and/or intellectual disability. Only facial features typical of BCNS, except in those with prominent midforeheads secondary to metopic craniosynostosis, were shared among the 10 patients. The deletions in these individuals ranged from 352  kb to 20.5  Mb in size, the largest spanning 9q21.33 through 9q31.2. There was significant overlap of the deleted segments among most of the patients. The smallest common regions shared among the deletions were identified in order to localize putative candidate genes that are potentially responsible for each of the non-BCNS features. These were a 929  kb region for metopic craniosynostosis, a 1.08  Mb region for obstructive hydrocephalus, and a 1.84  Mb region for macrosomia. Additional studies are needed to further characterize the candidate genes within these regions.

Fatal acute encephalopathy in two siblings: a distinct hereditary entity?

Viral infections particularly the influenza infection can be associated with significant central nervous system complications. The encephalopathy associated with viral infection may not be necessarily due to invasion by the microorganism but rather the hypercytokinemic response of the host. Individuals with certain genetic background are postulated to be at risk of this complication. Recent works in this area are aiming to elucidate the molecular mechanism and genetic susceptibility of this condition. Familial cases of infection associated encephalopathy indicate strong hereditary predisposition in some individuals. We describe a family with two siblings who developed fatal acute encephalopathy following respiratory tract infection of likely viral etiology.