Supplementary Material for: Double Genetic Diagnosis Involving MECP2 and EPHB4 in a Child with Neurodevelopmental Delay and Vascular Anomalies: A Case Report

Background:
Double genetic diagnoses are increasingly identified with the advent of genome-wide sequencing techniques. While MECP2 mutations are associated with Rett syndrome and EPHB4 mutations with vascular malformation syndromes, their co-occurrence has not been previously described.
Case Presentation:
We describe an 8-year and 2-month-old girl presenting with global developmental delay, autism spectrum disorder (ASD), and stereotypic behaviors, along with multiple well-demarcated cutaneous vascular lesions. Although she had no clinical seizures, EEG revealed epileptiform discharges. Physical examination showed dysmorphic features and vascular anomalies, including telangiectatic pink to red macular vascular lesions. Whole exome sequencing (WES) identified two de novo heterozygous pathogenic variants: a missense mutation in MECP2 (c.433C>T; p.Arg145Cys), a gene classically implicated in Rett syndrome, and a nonsense mutation in EPHB4 (c.1093C>T; p.Arg365Ter), which has been previously associated with capillary malformation–arteriovenous malformation syndrome type 2 (CM-AVM2). The neurodevelopmental findings, while consistent with the broader spectrum of MECP2-related disorders, along with coexisting vascular anomalies, were best accounted for by a dual genetic diagnosis involving both MECP2 and EPHB4.
Conclusion:
This case underscores the diagnostic value of considering dual genetic diagnoses in patients with complex phenotypes and highlights the role of WES in uncovering multilocus variation, thereby expanding the known phenotypic spectrum associated with MECP2 and EPHB4 mutations.