Congenital Central Hypoventilation Syndrome Caused by A de novo RET Pathogenic Variant

Introduction: Congenital central hypoventilation syndrome (CCHS) is a rare life-threatening disorder characterized by a failure in physiologic autonomic control of breathing resulting in apnoea, hypoxemia, and hypoventilation episodes, associated to a large spectrum of autonomic nervous system dysfunctions. Despite this condition is most likely caused by mutations in the PHOX2B gene, other genes have been found responsible for CCHS in rare cases. Case report: We report a 15-month-old toddler presenting episodes of central and obstructive apnoea with cyanosis, hypertonia, hypercapnia, and cyanotic breath-holding spells. The CCHS diagnosis was supported by central desaturating apnoea/hypopneas episodes during rapid eye movement sleep and obstructive apnoea in polysomnography, as well as by the presence of hypoxia and hypercapnia in arterial blood gas during critical episodes. Autonomic dysregulation with sporadic profuse sweating and gastrointestinal dysmotility resulting in gastro-oesophageal reflux and chronic constipation were also associated. Next Generation Sequencing revealed the missense variant p.Met918Thr in the RET gene.Conclusion: This case, identifying a de novo pathogenic variant in the RET gene, highlights the importance of using clinical exome sequencing or a panel of genes associated with the specific disease, rather than looking for mutations in the single most frequently correlated gene.