Lethal neonatal respiratory failure due to biallelic variants in BBS1 and monoallelic variant in TTC21B.

BACKGROUND: Bardet-Biedl syndrome (BBS) is a rare, autosomal recessive ciliopathy characterized by early onset retinal dystrophy, renal anomalies, postaxial polydactyly, and cognitive impairment with considerable phenotypic heterogeneity. BBS results from biallelic pathogenic variants in over 20 genes that encode key proteins required for the assembly or primary ciliary functions of the BBSome, a heterooctameric protein complex critical for homeostasis of primary cilia. While variants in BBS1 are most frequently identified in affected individuals, the renal and pulmonary phenotypes associated with BBS1 variants are reportedly less severe than those seen in affected individuals with pathogenic variants in the other BBS-associated genes. CASE-DIAGNOSIS: We report an infant with severe renal dysplasia and lethal pulmonary hypoplasia who was homozygous for the most common BBS1 pathogenic variant (c.1169 T > G; p.M390R) and also carried a predicted pathogenic variant in TTC21B (c.1846C > T; p.R616C), a genetic modifier of disease severity of ciliopathies associated with renal dysplasia and pulmonary hypoplasia. CONCLUSIONS: This report expands the phenotypic spectrum of BBS with the first infant with lethal neonatal respiratory failure associated with biallelic, pathogenic variants in BBS1 and a monoallelic, predicted pathogenic variant in TTC21B. BBS should be considered among the ciliopathies in the differential diagnosis of neonates with renal dysplasia and severe respiratory failure.

Respiratory failure in a term infant with cis and trans mutations in ABCA3.

A full-term female neonate presented with persistent respiratory failure and radiologic studies consistent with surfactant deficiency. Sequencing of the ATP-binding cassette transporter A3 gene (ABCA3) revealed three mutations: R280C, V1399M and Q1589X. The infant underwent bilateral lung transplantation at 9 months of age and is alive at 3 years of age. Parental sequencing demonstrated that two of the mutations (R280C and Q1589X) were oriented on the same allele (cis), whereas V1399M was oriented on the opposite allele (trans). As more than one mutation in ABCA3 can be present on the same allele, parental studies are needed to determine allelic orientation to inform clinical decision making and future reproductive counseling.

Genetic variation in MKL2 and decreased downstream PCTAIRE1 expression in extreme, fatal primary human microcephaly.

The genetic mechanisms driving normal brain development remain largely unknown. We performed genomic and immunohistochemical characterization of a novel, fatal human phenotype including extreme microcephaly with cerebral growth arrest at 14-18 weeks gestation in three full sisters born to healthy, non-consanguineous parents. Analysis of index cases and parents included familial exome sequencing, karyotyping, and genome-wide single nucleotide polymorphism (SNP) array. From proband, control and unrelated microcephalic fetal cortical tissue, we compared gene expression of RNA and targeted immunohistochemistry. Each daughter was homozygous for a rare, non-synonymous, deleterious variant in the MKL2 gene and heterozygous for a private 185 kb deletion on the paternal allele, upstream and in cis with his MKL2 variant allele, eliminating 24 CArG transcription factor binding sites and MIR4718. MKL1 was underexpressed in probands. Dysfunction of MKL2 and its transcriptional coactivation partner, serum response factor (SRF), was supported by a decrease in gene and protein expression of PCTAIRE1, a downstream target of MKL2:SRF heterodimer transcriptional activation, previously shown to result in severe microcephaly in murine models. While disruption of the MKL2:SRF axis has been associated with severe microcephaly and disordered brain development in multiple model systems, the role of this transcription factor complex has not been previously demonstrated in human brain development.

Increased risk for respiratory distress among white, male, late preterm and term infants.

OBJECTIVE: To determine whether race/ethnicity and sex independently increase risk of respiratory distress syndrome (RDS) in late preterm and term infants. STUDY DESIGN: Using a cohort design, we studied the risk of RDS associated with race/ethnicity and sex in infants with gestational age (GA) 34 to 42 weeks born between 1 January 2000 and 31 December 2009 (n=286 454) within 12 hospitals in the Northern California Kaiser Permanente Medical Care Program. RESULT: Male sex (adjusted odds ratio (aOR) 1.68; 95% confidence interval 1.45 to 1.93) and White race/ethnicity (vs Asians (aOR 0.57; 95% confidence interval 0.47 to 0.70), Blacks (aOR 0.66; 95% confidence interval 0.50 to 0.87), and Hispanics (aOR 0.76; 95% confidence interval 0.64 to 0.90)) independently increase risk for RDS regardless of GA. A GA <39 weeks, operative delivery, maternal diabetes, and chorioamnionitis also increased RDS risk in this cohort. CONCLUSION: Male sex and White race/ethnicity independently increase risk for RDS in late preterm and term infants. Timing of elective delivery should acknowledge these risks.

Surfactant protein-C promoter variants associated with neonatal respiratory distress syndrome reduce transcription.

Dominant mutations in coding regions of the surfactant protein-C gene, SFTPC, cause respiratory distress syndrome (RDS) in infants. However, the contribution of variants in noncoding regions of SFTPC to pulmonary phenotypes is unknown. By using a case-control group of infants > or =34 weeks gestation (n = 538), we used complete resequencing of SFTPC and its promoter, genotyping, and logistic regression to identify 80 single nucleotide polymorphisms (SNPs). Three promoter SNPs were statistically associated with neonatal RDS among European descent infants. To assess the transcriptional effects of these three promoter SNPs, we selectively mutated the SFTPC promoter and performed transient transfection using MLE-15 cells and a firefly luciferase reporter vector. Each promoter SNP decreased SFTPC transcription. The combination of two variants in high linkage dysequilibrium also decreased SFTPC transcription. In silico evaluation of transcription factor binding demonstrated that the rare allele at g.-1167 disrupts a SOX (SRY-related high mobility group box) consensus motif and introduces a GATA-1 site, at g.-2385 removes a MZF-1 (myeloid zinc finger) binding site, and at g.-1647 removes a potential methylation site. This combined statistical, in vitro, and in silico approach suggests that reduced SFTPC transcription contributes to the genetic risk for neonatal RDS in developmentally susceptible infants.

Population-based screening for rare mutations: high-throughput DNA extraction and molecular amplification from Guthrie cards.

To determine the population-based frequency of a rare mutation (the 121ins2 mutation in the surfactant protein B gene), we developed high-throughput techniques to extract reliably and rapidly amplifiable DNA from Guthrie cards. Using a 3-mm punch from each of 10,044 Guthrie cards obtained from the Missouri Department of Health, we extracted DNA with deionized water by heating in the presence of 2% Chelex in a 96-well format. Average yield of DNA from each punch was 52.6 +/- 21 microg. Using 36mer primers and a 10-microL reaction volume, we amplified a 354-bp fragment of the surfactant protein B gene that contained the mutation and identified the mutation by its susceptibility to restriction enzyme digestion with SfuI. The procedure required 5 h per 96 samples but only 2 h of technician time. The amplification rate on the first attempt was 99.2%. Based on detection of eight individuals heterozygous for the mutation (confirmed by direct sequencing), we estimate the allele frequency to be 0.8/1000 individuals, an estimate not significantly different from previous estimates based on independent methods. High-throughput DNA extraction and amplification will permit establishment of DNA banks as well as efficient estimation of population-based genotype frequency for both rare and common genetic disorders.

Alveolar capillary dysplasia with misalignment of pulmonary veins and anterior segment dysgenesis of the eye: a report of a new association and review of the literature.

The association of alveolar capillary dysplasia with misalignment of pulmonary veins (ACD-MPV) and ocular abnormalities has not been previously reported. We present a case of ACD-MPV and anterior segment dysgenesis of the eye in a full-term infant as well as a review of the relevant literature.

Genetic disorders of neonatal respiratory function.

Genetic risk for respiratory distress in infancy has been recognized with increasing frequency in neonatal intensive care units. Reports of family clusters of affected infants and of ethnic- and gender-based respiratory phenotypes point to the contribution of inheritance. Similarly, different outcomes among gestationally matched infants with comparable exposures to oxygen, mechanical ventilation, or nutritional deficiency also suggest a genetic risk for respiratory distress. Examples of inherited deficiency of surfactant protein B in both humans and genetically engineered murine lineages illustrate the importance of identifying markers of genetic risk. In contrast to developmental, inflammatory, or nutritional causes of respiratory distress that may resolve as infants mature, genetic causes result in both acute and chronic (and potentially irreversible) respiratory failure. The availability of clinically useful genetic markers of risk for respiratory distress in infancy will permit development of rational strategies for treatment of genetic lung disorders of infancy and more accurate counseling of families whose infants are at genetic risk for development of respiratory distress at birth or during early childhood. We review examples of genetic variations known to be associated with or cause respiratory distress in infancy.

Population-based estimates of surfactant protein B deficiency.

OBJECTIVE: Surfactant protein B deficiency is a lethal cause of respiratory distress in infancy that results most commonly from a homozygous frameshift mutation (121ins2). Using independent clinical ascertainment and molecular methods in different populations, we sought to determine allele frequency. STUDY DESIGN: Using clinical characteristics of the phenotype of affected infants, we screened the Missouri linked birth-death database (n = 1 052 544) to ascertain potentially affected infants. We used molecular amplification and restriction enzyme digestion of DNA samples from a metropolitan New York birth cohort (n = 6599) to estimate allele frequency. RESULTS: The point estimate and 95% confidence interval of the 121ins2 allele frequency in the Missouri cohort are 1/1000 individuals (.03-5.6/1000) and in the New York cohort are.15/1000 (. 08-.25/1000). These estimates are not statistically different. CONCLUSIONS: The close approximation of these independent estimates suggests accurate gene frequency (approximately one 121ins2 mutation per 1000-3000 individuals) despite its rare occurrence and that this mutation does not account for the majority of full-term infants with lethal respiratory distress.

Hyaline membrane disease is underreported in a linked birth-infant death certificate database.

OBJECTIVE: This study compared the Missouri State Department of Health linked birth-infant death certificate database and medical records with respect to recording hyaline membrane disease in very low-birth-weight infants. METHODS: We reviewed the records for all 976 infants weighing 500 to 1500 g who were born to St. Louis, Mo, residents in 1989, 1991, and 1992. RESULTS: Eighteen percent of the birth certificates and 54% of the medical records documented hyaline membrane disease, resulting in 34% sensitivity and 99% specificity. CONCLUSIONS: The Missouri State Department of Health birth-infant death certificate database underestimates the incidence of hyaline membrane disease, which suggest that national statistics for the disease are also underestimated.

Antenatal steroids and intraventricular hemorrhage after premature rupture of membranes at 24-28 weeks' gestation.

To determine whether antenatal corticosteroid administration after midtrimester premature rupture of membranes (PROM) reduces the incidence or severity of neonatal intraventricular hemorrhage, we identified a cohort of infants delivered between 24 to 28 weeks gestation (n = 75) by mothers with PROM. Information was obtained from a computerized database (n = 3716) of all newborns admitted to the neonatal intensive care unit at a single medical center from 1991 to 1996. We reviewed records of each mother-infant pair to determine antenatal corticosteroid administration, presence, and severity of neonatal intraventricular hemorrhage, and frequency of infectious complications. Using a logistic regression model, antenatal corticosteroid administration was associated with a significantly reduced risk of severe (grade 3-4) intraventricular hemorrhage (0.1 odds ratio, 0.006-0.57, 95% confidence interval), but not a reduced incidence of intraventricular hemorrhage (grade 1-4, 0.4 odds ratio, 0.12-1.05, 95% confidence interval).

Risk status at discharge and cause of death for postneonatal infant deaths: a total population study.

OBJECTIVES: To obtain population-based, clinical information regarding potentially modifiable factors contributing to death during the postneonatal period (28 to 364 days), we examined all postneonatal infant deaths in four areas of the United States to determine: (1) the cause of death from clinical and autopsy data rather than vital statistics, (2) whether death occurred during initial hospitalization or after discharge, and (3) the portion of postneonatal mortality attributable to infants who left the hospital with identified high-risk medical conditions. DESIGN AND SETTING: Retrospective medical record review of all postneonatal infant deaths with birth weights greater than 500 g (total N = 386) born to mothers residing in: (1) the city of Boston (1984 and 1985, N = 55), (2) the city of St Louis and contiguous areas (1985 and 1986, N = 123), (3) San Diego County (1985, N = 112), and (4) the state of Maine (1984 and 1985, N = 96). Deaths were identified using linked birth and death vital statistics, and medical record audits of infants' and mothers' charts were performed. Causes of death were obtained from medical record review in conjunction with autopsy if performed (72%, N = 278), medical record alone (17%, N = 67), or vital statistics if no other source was available (11%, N = 41). The medical conditions at the time of discharge for each infant were reviewed and, if judged to confer an increased risk of morbidity or mortality, were classified as high risk. RESULTS: The causes of death were sudden infant death syndrome (47%, N = 181), congenital conditions (20%, N = 77), prematurity-related conditions (11%, N = 43), infections (9%, N = 34), external causes (including injuries, drownings, ingestions, and burns) (7%, N = 25), and other (6%, N = 23). In 24% of congenital and 25% to 44% of prematurity-related deaths, infection was the acute or associated cause of death. Infants born to black mothers were more likely than those born to white mothers to die during the postneonatal period of all major causes of death (7.3 per 1000 vs 3.0 per 1000). Overall, 18% (N = 68) of deaths occurred to infants who never left the hospital; 79% (N = 305) of the infants were discharged before death; and discharge status was unknown in 3% (N = 13). Eighty-one percent of all infants with prematurity-related postneonatal deaths were never discharged, and of the total infants who were initially discharged, only 1% (N = 4) subsequently died of prematurity-related causes. Of all postneonatal deaths, only 16% (N = 62) left the hospital with identified high-risk medical conditions. CONCLUSIONS: These findings suggest that the etiology of postneonatal mortality is heterogeneous, with significant complexity in attributing specific causes of death and making designations of "preventability." The vast majority of infants who died of prematurity-related postneonatal causes never left the hospital, and only a small percentage of all infants that left the hospital before death were identified as being at high medical risk. Therefore, strategies for further decreasing postneonatal mortality must link high-risk follow-up programs to more comprehensive strategies that address risk throughout pregnancy and early childhood.

Lung transplantation for treatment of infants with surfactant protein B deficiency.

OBJECTIVE: To evaluate lung transplantation for treatment of surfactant protein B (SP-B) deficiency. STUDY DESIGN: We compared surfactant composition and function from pretransplantation and posttransplantation samples of bronchoalveolar lavage fluid, somatic and lung growth, neurodevelopmental progress, pulmonary function, and pulmonary immunohistology in 3 infants with SP-B deficiency who underwent bilateral lung transplantation at 2 months of age and 3 infants who underwent lung transplantation for other reasons. RESULTS: Two years after transplantation, the 2 surviving infants with SP-B deficiency exhibited comparable somatic growth and cognitive development to the comparison infants. All infants had delays in gross motor development that improved with time. Both groups have exhibited normal gas exchange, lung growth, and pulmonary function. The SP-B-deficient infants have also exhibited normal SP-B expression and pulmonary surfactant function after lung transplantation. In two SP-B-deficient infants antibody to SP-B developed. No pathologic consequences of this antibody were identified. CONCLUSIONS: Apart from the development of anti-SP-B antibody, the outcomes for SP-B-deficient infants after lung transplantation are similar to those of infants who undergo lung transplantation for other reasons. Lung transplantation offers a successful interim therapy until gene replacement for this disease is available.

The influence of the wider use of surfactant therapy on neonatal mortality among blacks and whites.

BACKGROUND: Surfactant therapy reduces morbidity and mortality among premature infants with the respiratory distress syndrome (RDS). Fetal pulmonary surfactant matures more slowly in white than in black fetuses, and therefore RDS is more prevalent among whites than among blacks. We reasoned that the increased use of surfactant after its approval by the Food and Drug Administration (FDA) in 1990 might have reduced neonatal mortality more among whites than among blacks. METHODS: We merged vital-statistics information for all 1563 infants with very low birth weights (500 to 1500 g) born from 1987 through 1989 or in 1991 and 1992 to residents of St. Louis with clinical data from the four neonatal intensive care units in the St. Louis area; we then compared neonatal mortality during two periods, one before and one after the FDA's approval of surfactant for clinical use (1987 through 1989 and 1991 through 1992). RESULTS: The use of surfactant increased by a factor of 10 between 1987 through 1989 and 1991 through 1992. The neonatal mortality rate among all very-low-birth-weight infants decreased 17 percent, from 220.3 deaths per 1000 very-low-birth-weight babies born alive (in 1987 through 1989) to 183.9 per 1000 (in 1991 through 1992; P = 0.07). This decrease was due to a 41 percent reduction in the mortality rate among white newborns with very low birth weights (from 261.5 per 1000 to 155.5 per 1000; P = 0.003). In contrast, among black infants, the mortality rate for very-low-birth-weight infants did not change significantly (195.6 per 1000 and 196.8 per 1000). The relative risk of death among black newborns with very low birth weights as compared with white newborns with similar weights was 0.7 from 1987 through 1989 and 1.3 from 1991 through 1992 (P = 0.02). The differences in mortality were not explained by differences in access to surfactant therapy, by differences in mortality between black and white infants who received surfactant, or by differences in the use of antenatal corticosteroid therapy. CONCLUSIONS: After surfactant therapy for RDS became generally available, neonatal mortality improved more for white than for black infants with very low birth weights.

Umbilical cord ulceration as a cause of hypoxic-ischemic encephalopathy: report of a case and review of the literature.

We report a case of hypoxic-ischemic injury caused by acute hemorrhage from an umbilical cord ulceration in a newborn infant with an antenatal diagnosis of small bowel obstruction. Recognition of the association between umbilical cord ulceration and small bowel obstruction may alter obstetric and delivery room management.

Phenylalanine hydroxylase activity in preterm infants: is tyrosine a conditionally essential amino acid?

To assess the production of the nonessential amino acid tyrosine in preterm infants, we estimated the activity of phenylalanine hydroxylase (PAH) in three groups of infants by measuring the conversion of phenylalanine to tyrosine, using a model based on a primed constant 200-min intravenous infusion of [2H5]phenylalanine. We determined the isotopic enrichments of [2H5]phenylalanine and [2H4]tyrosine by selected-ion-monitoring gas chromatography-mass spectrometry (GCMS). Group 1 (n = 7, mean gestational age 29.7 +/- 1.5 wk, mean birth weight 1.4 +/- 0.4 kg) was studied during the first 4 d of life before initiation of amino acid nutrition. Group 2 (n = 7, mean gestational age 29.7 +/- 1.5 wk, mean birth weight 1.4 +/- 0.4 kg) was studied at 4-6 d of life after receiving amino acid nutrition. Group 3 (n = 4, mean gestational age 28.5 +/- 0.9 wk, mean birth weight 1.1 +/- 0.1 kg) was studied during the first 4 d of life after receiving amino acid nutrition. Calculated from the observed enrichments, phenylalanine conversion to tyrosine was 5.9 +/- 2.6, 19.4 +/- 8.8 and 11 +/- 1.8 mumol.kg-1l.h-1 in groups 1, 2, and 3, respectively. The rate of conversion of phenylalanine to tyrosine increased significantly after initiation of amino acid nutrition. We conclude that preterm infants are capable of converting phenylalanine to tyrosine. Provision of phenylalanine in the context of parenteral amino acid nutrition solution accelerated PAH conversion of phenylalanine to tyrosine, suggesting that the enzyme system is capable of responding normally to provision of substrate.(ABSTRACT TRUNCATED AT 250 WORDS)

School-based AIDS education for adolescents.

PURPOSE: To describe a program which utilizes medical students and persons with AIDS (PWAs) to provide for adolescents school-based education about acquired immunodeficiency syndrome (AIDS). METHODS: Two 1.5 hour classroom sessions were conducted by medical students and persons with AIDS for seventh and eighth grade students (n = 1,161 students) at two urban middle schools. In addition, a two hour informational session was provided for parents. A 49 question student health survey was used to evaluate adolescents' HIV knowledge, tolerance of persons with AIDS, and intentions to engage in human immunodeficiency virus (HIV) safe behaviors. RESULTS: Significant (p < 0.01) increases in HIV knowledge and tolerance of persons with AIDS were observed, which persisted for three months. A significant (p < 0.01) improvement in intention to engage in HIV-safe behaviors was observed but did not persist for three months. CONCLUSIONS: Medical students and persons with AIDS can provide school-based AIDS education to early adolescents.

Pathophysiology and treatment of surfactant protein-B deficiency.

Surfactant protein B (SP-B) deficiency is an inherited disease of full-term newborn infants which leads to lethal respiratory failure within the first year of life. Genetic analysis of affected infants has permitted identification of a mutation in the SP-B gene found in several unrelated kindreds which disrupts pulmonary surfactant composition and function. Lung transplantation has resulted in reconstitution of pulmonary surfactant function and long-term survival. SP-B deficiency represents the first opportunity to link physiologic characteristics of respiratory failure in infancy with specific molecular and cellular defects. This linkage will facilitate development of novel strategies for the treatment of neonatal respiratory diseases.