Further Delineation of Clinical Phenotype of <em>ZMYND11 </em>Variants in Patients with Neurodevelopmental Dysmorphic Syndrome and Hyperinsulinemic Hypoglycemia

Intellectual disability with speech delay and behavioural abnormalities as well as hypotonia, seizures, feeding difficulties and cra-niofacial dysmorphism are the main symptoms associated with pathogenic variants of ZMYND11 gene. The range of clinical mani-festations of ZMYND phenotype is constantly being expanded by new cases described in the literature. Here, we present 2 previ-ously unreported paediatric patients with neurodevelopmental features diagnosed with missense variants in ZMYND11 gene. It should be noted that one of the individuals manifested with hyperinsulinemic hypoglycaemia (HH), a symptom that was not de-scribed before in published works. Although the reason for the occurrence of HH in our proband is not clear, it is likely that it broadens the spectrum of symptoms characteristic of ZMYND11 syndrome. Thus, this paper contributes to extending the range of possible manifestations of ZMYND disease and further supports its association with neurodevelopmental challenges.