C61-07 Unique Genetic Inheritance of a 6-Month-Old Infant With Situs Inversus Totalis and Primary Ciliary Dyskinesia (PCD)

We present the case of a 6-month-old male diagnosed with situs inversus totalis, dextrocardia, and primary ciliary dyskinesia due to a homozygous variant in the DNAI1 gene (c.1490 G>A, p.G497D), arising from maternal uniparental disomy (UPD) of chromosome 9 and the presence of a likely pathogenic variant in the DNAI1 gene, consistent with his clinical presentation. The patient, born at 38 weeks and 6 days via spontaneous vaginal delivery, initially required neonatal intensive care for respiratory distress. Imaging studies revealed situs inversus totalis with dextrocardia and a right-sided stomach and liver. He was discharged with supplemental oxygen and airway clearance but is no longer requiring supplemental oxygen. PCD is associated with abnormal ciliary structure and function that leads to chronic otosinopulmonary disease, abnormal flagellar structure resulting in abnormal sperm motility, and can present with or without situs inversus. Currently, there are 54 causative genes that are identified. Diagnosis relies on combination of tests including nasal nitric oxide (nNO) measurements, high-speed videomicroscopy analysis (HSVMA), immunofluorescent staining, axonemal ultrastructure analysis via transmission electron microscopy (TEM), and genetic testing. Identification of biallelic, disease-causing variants in a single, autosomal recessive PCD gene (or a single pathogenic variant in one of four known X-linked or autosomal dominant PCD genes) is evolving to become the gold standard diagnostic test for PCD Maternal uniparental disomy (UPD) of chromosome 9 has been reported in children with intrauterine growth restriction with favorable outcomes; other individuals have had normal prenatal growth. There are no known imprinted genes on chromosome 9 that raise the concern for an imprinting disorder with the finding of maternal UPD of chromosome 9. This was likely a sporadic occurrence, and we expect the recurrence risk to be low. Given the increased likelihood of autosomal recessive conditions on chromosome 9 because of the UPD, he may need reanalysis of his genetics if he shows new concerns.This case is unique in that the genetic inheritance of PCD is due to UPD. There was only one other case reported of a patient with PCD and cystic fibrosis (CF) with UPD inheritance of the same chromosome 7.