A Study on the Genetics of Primary Ciliary Dyskinesia.

Primary ciliary dyskinesia (PCD) is a poorly understood disorder. It is primarily autosomal recessive and is prevalent in tribal communities of the United Arab Emirates due to consanguineous marriages. This retrospective study aimed to assess the pathogenicity of the genetic variants of PCD in indigenous patients with significant clinical respiratory problems. Pathogenicity scores of variants obtained from the chart review were consolidated using the Ensembl Variant Effect Predictor. The multidimensional dataset of scores was clustered into three groups based on their pathogenicity. Sequence alignment and the Jensen-Shannon Divergence (JSD) were generated to evaluate the amino acid conservation at the site of the variation. One-hundred and twelve variants of 28 genes linked to PCD were identified in 66 patients. Twenty-two variants were double heterozygous, two triple heterozygous, and seven homozygous. Of the thirteen novel variants, two, c.11839 + 1G > A in dynein, axonemal, heavy chain 11 (DNAH11) and p.Lys92Trpfs in dynein, axonemal, intermediate chain 1 (DNAI1) were associated with dextrocardia with situs inversus, and one, p.Gly21Val in coiled-coil domain-containing protein 40 (CCDC40), with absent inner dynein arms. Homozygous C1orf127:p.Arg113Ter (rs558323413) was also associated with laterality defects in two related patients. The majority of variants were missense involving conserved residues with a median JSD score of 0.747. Homology models of two deleterious variants in the stalk of DNAH11, p.Gly3102Asp and p.Leu3127Arg, revealed structural importance of the conserved glycine and leucine. These results define potentially damaging PCD variants in the region. Future studies, however, are needed to fully comprehend the genetic underpinnings of PCD.

A Single-Institution Experience in the Use of Chest Radiographs for Hospitalized Children Labeled as Asthma Exacerbation.

Background: Risks of diagnostic radiation have become more notable lately, particularly in young children with chronic medical conditions. This study reports on the cumulative radiation from chest radiographs in children with asthma. Its main purpose was to review our current practice and suggest minimizing the use of chest radiographs. Methods: The study was retrospective and conducted at a pediatric tertiary center. Eligibility criteria included children 2-15 y, admitted between January 2017 and December 2018 for asthma management. Results: Of the 643 children admitted as "asthma exacerbation," 243 [40% females; age (mean ± SD) 5.4±3.3 y] met the study criteria for inclusion. Ninety-two (38%) children had a temperature of 38.8±0.7°C on the day of admission. Antibiotics were prescribed for 148 (61%) children, mainly for presumed pneumonia. Chest radiographs were requested for 214 (88%) children, mainly on the day of admission. Only 38 (18%) chest radiographs showed focal/multifocal pneumonia justifying antibiotic use. Significant predictors for requesting chest radiographs were antibiotic use for presumed pneumonia, lower oxygen saturation at presentation, and a requested blood culture. The rate of chest radiographs per year was negatively related to the child's age; the younger the child the higher the rate (model coefficient -0.259, P < 0.001). For children < 5 y, the rate of chest radiographs was 1.39 ± 1.21/y and radiation dose 0.028 ± 0.025 mSv/y. The corresponding rates for children ≥5 y were 0.78 ± 0.72/y and 0.008 ± 0.007 mSv/y, respectively (P < 0.001). Conclusion: Chest radiographs were commonly requested for children with asthma, especially younger children. Prospective studies are necessary to measure the impact of this practice on the children's health.

Genetic variants of small airways and interstitial pulmonary disease in children.

Genetic variants of small airways and interstitial pulmonary disease have not been comprehensively studied. This cluster of respiratory disorders usually manifests from early infancy ('lung disease in utero'). In this study, 24 variants linked to these entities are described. The variants involved two genes associated with surfactant metabolism dysfunction (ABCA3 and CSF2RB), two with pulmonary fibrosis (MUC5B and SFTP), one with bronchiectasis (SCNN1B), and one with alpha-1-antitrypsin deficiency (SERPINA1). A nonsense variant, MUC5B:c.16861G > T, p.Glu5621*, was found in homozygous state in two siblings with severe respiratory disease from birth. One of the siblings also had heterozygous SFTPA1:c.675C > G, p.Asn225Lys, which resulted in a more severe respiratory disease. The sibling with only the homozygous MUC5B variant had lung biopsy, which showed alveolar simplification, interstitial fibrosis, intra-alveolar lipid-laden macrophages, and foci of foreign body giant cell reaction in distal airspaces. Two missense variants, MUC5B:c.14936 T > C, p.Ile4979Thr (rs201287218) and MUC5B:c.16738G > A, p.Gly5580Arg (rs776709402), were also found in compound heterozygous state in two siblings with severe respiratory disease from birth. Overall, the results emphasize the need for genetic studies for patients with complex respiratory problems. Identifying pathogenic variants, such as those presented here, assists in effective family counseling aimed at genetic prevention. In addition, results of genetic studies improve the clinical care and provide opportunities for participating in clinical trials, such as those involving molecularly-targeted therapies.

Genetic variants in children with chronic respiratory diseases.

Founder mutations and autosomal recessive (AR) disorders are common in the Arabian Peninsula due to frequent consanguineous marriages. As a result, the pulmonary service at Tawam Hospital (Al Ain, UAE) routinely requests genetic testing for children with persistent (unexplained) respiratory problems. The main purpose of this report was to underscore the usefulness of these tests. Ten children with severe respiratory diseases due to complex genetic findings are described here. Forty-one variants (six novel) were detected, averaging four per patient (range: 1-9). Seven (17%) variants were homozygous and 34 (83%) heterozygous; some variants were known to show monoallelic expression. Using binomial probability distribution, the fetal-risk for having AR disorder(s) as a function of the number of shared variants by a couple ranged from 0.25 (having one shared variant) to 0.9249 (having nine shared variants). In cultures where increased size of homozygous genomic segments is common, children often have multiple variants that could cause complex clinical phenotypes. Identifying pathogenic variants assists in clinical care, family counseling, and disease prevention through genetic screening.