BCL11B-related disorder in two canadian children: Expanding the clinical phenotype

The product of the BCL11B (B-Cell Leukemia 11) gene is a bi-functional transcriptional regulator that can act as either a repressor or an activator. It plays an important role in the development of the nervous, immune, and cutaneous systems, and is also involved in dental and craniofacial development. BCL11B-Related Disorder (BCL11BRD) is a novel rare neurodevelopmental disorder associated with mutations in BCL11B. A total of 17 patients have been described in the literature thus far. The main symptoms of BCL11BRD include global developmental delay, speech impairment, dental anomalies, feeding difficulties, refractive errors, dysmorphic features, and immunological abnormalities. In this report, we describe two Canadian girls, with pathogenic de novo BCL11B variants, both diagnosed via exome sequencing. One of the patients had global developmental delay, dental anomalies, dysmorphic features, dyskinesia and hypotonia; the latter two symptoms have not been previously reported in patients with BCL11BRD. She also had dysgenesis of corpus callosum and dilatation of the frontal horns of lateral ventricles, a brain anomaly that has been previously reported in only one other patient. The second patient had developmental delay, dysmorphic features, spasticity in lower limbs and dental anomalies. Our report contributes to the knowledge of the BCL11BRD, expands the clinical phenotype, and can also aid with genetic counseling of newly identified patients.