An episode of acute encephalopathy with biphasic seizures and late reduced diffusion followed by hemiplegia and intractable epilepsy observed in a patient with a novel frameshift mutation in HNRNPU.

Microdeletions in the 1q44 region encompassing the HNRNPU gene have been associated with infantile spasms and hemiconvulsion-hemiplegia-epilepsy syndrome. Recent studies have revealed that heterozygous HNRNPU variants resulted in early onset epilepsy and severe intellectual disability. A de novo frameshift mutation in HNRNPU was identified in a 5-year-old boy with developmental delay associated with Rett-like features including stereotypic hand movements and respiratory abnormalities with episode of apnea and hyperpnea followed by falling. He also showed an episode of acute encephalopathy with biphasic seizures and late reduced diffusion followed by hemiplegia and intractable epilepsy. Unique and variable clinical features are related to loss-of-function or haploinsufficiency of HNRNPU.