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Abstract MRPS23 is a nuclear gene encoding a mitochondrial ribosomal protein. A patient with a mitochondrial disorder was found to carry a variant in MRPS23. More cases are necessary to establish MRPS23 as a mitochondrial disease gene. Of 5134 exomes performed in our center, we identified five independent patients who had similar clinical manifestations and were homozygous for the same germline variant c.119C>T; p.P40L in MRPS23. Detailed clinical findings, mitochondrial enzyme activity assays from cultured skin fibroblasts, PCR-Sanger-sequencing, and variant age estimation were performed. Their available family members were also studied. Eight members homozygous for the MRPS23 p.P40L were identified. All were from Hmong hilltribe. Seven presented with alteration of consciousness and recurrent vomiting, while the eighth who was a younger brother of a proband was found pre-symptomatically. Patients showed delayed growth and development, hearing impairment, hypoglycemia, lactic acidosis, and liver dysfunction. In vitro assays of cultured fibroblasts showed combined respiratory chain complex deficiency with low activities of complexes I and IV. PCR-Sanger-sequencing confirmed the variant, which was estimated to have occurred 1550 years ago. These results establish the MRPS23-associated mitochondrial disorder inherited in an autosomal recessive pattern and provide insight into its clinical and metabolic features.

Abstract Alveolar capillary dysplasia with misalignment of the pulmonary veins (ACDMPV) is a rare congenital diffuse lung disorder, with a fatal course during the neonatal period. We describe an 18‐month‐old boy who presented with respiratory syncytial virus pneumonia and pulmonary hypertensive crisis requiring extracorporeal membrane oxygenation. Exome sequencing revealed a FOXF1 frameshift variant, NM_001451.2:c.995_998delACTC, inherited from his asymptomatic mother. Genetic findings were compatible with histopathology findings from a lung biopsy. Based on the disease course, histopathology, and outcomes of this case, we believe ACDMPV should be considered a possibility in an infant presenting with hypoxemic respiratory failure, resistant pulmonary hypertension, and vasodilator‐induced pulmonary edema. Genetic testing can contribute to the diagnostic process.

Wolman disease is a very rare autosomal recessive genetic disorder. The patients have the typical clinical finding of hepatosplenomegaly but with an abnormal lipid profile of high levels of total cholesterol (TC), triglycerides, and low-density lipoprotein cholesterol (LDL-C), but a low level of high-density lipoprotein cholesterol (HDL-C). We report a 1-month-old boy with Wolman disease who had hepatosplenomegaly but with an atypical abnormal lipid profile of low TC level, and very low levels of both LDL-C and HDL-C. The genetic study revealed a compound heterozygous mutation of the LIPA gene, leading to the confirmed diagnosis of Wolman disease.

Autism spectrum disorder (ASD) is a group of neurodevelopmental disorders which are etiologically heterogeneous. Chromosomal microarray is now recommended as the first-tier clinical diagnostic test for ASD. We performed chromosomal microarray in 16 Thai patients with ASD using an Illumina HumanCytoSNP-12 v2.1 array and found one case with uniparental disomy (UPD) of chromosome 15. Methylation-specific PCR showed abnormal methylation of the maternal SNRPN allele. Haplotype analysis revealed that the patient had received both chromosomes 15 from his father. These results were consistent with Angelman syndrome. However, his clinical features had no clinical significance for classic Angelman syndrome. He had first presented at the pediatric clinic with no speech, poor social interaction skills and repetitive behaviors consistent with ASD based on the DSM-IV criteria at 2 years of age and later confirmed by ADOS at 5 years of age. He was strikingly overweight but had no dysmorphic facies, seizures nor ataxia and was diagnosed as non-syndromic ASD, a diagnosis which was believed until at 10 years of age, his DNA was included for analysis in this current cohort study. Our findings suggest that ASD patients with unknown etiology should be considered for methylation-specific PCR testing for Angelman syndrome where chromosomal microarray is not available. In the study, we also review the clinical features of Angelman syndrome caused by UPD and the frequency of ASD in individuals with Angelman syndrome.