Patient and Family Reported Clinical Picture of IRF2BPL-Related Disorders.

IRF2BPL-related disorder is a neurodevelopmental disorder caused by heterozygous variants in the IRF2BPL (Interferon Regulatory Factor 2 Binding Protein-Like) gene. The few reports available in the literature suggest that common symptoms include developmental delay, intellectual disability, and developmental regression. Although emerging reports suggest broad relationships between variant class/location and severity, genotype-phenotype correlations remain incompletely defined. We developed a retrospective and prospective patient-reported survey to assess diagnostic information, presenting symptoms, and longitudinal follow-up of neurological symptoms for up to two years. Clinical information was available for all 32 participants and was highly variable in regards to age at symptom onset, severity of neurologic manifestations, and progressivity. For 27 of the 32 participants, diagnostic genetic test results were available. Genetic mutation analysis revealed 22 individuals with truncating variants and five participants with unique missense variants in IRF2BPL. The study data support the hypothesis that IRF2BPL missense variants are associated with a less severe disease presentation and progression than participants with truncating variants. The purpose of this study is to further define IRF2BPL-related disorder and provide more clinical and molecular insight into this ultra-rare disease.