Introduction: HNRNPU-related neurodevelopmental disorder (HNRNPU-NDD), also called early infantile epileptic encephalopathy-54 (EIEE54) syndrome, is a recently identified extremely rare disorder caused by pathogenic variations in the HNRNPU gene. It is characterized by global developmental delay (in which speech is disproportionately affected), seizures, intellectual disability, and behavioral abnormalities. We aimed to present a case with HNRNPU gene mutation, a extremely rare cause of developmental delay, who presented with speech delay. Case report: A 10-year-old girl was admitted to our outpatient clinic due to speech delay and self-mutilation. On physical examination, she had mild facial dysmorphic features, microcephaly and global developmental delay. The detailed biochemical and metabolic evaluations were unremarkable. Electroencephalography was normal. Cranial MRI showed inferior vermian hypoplasia and mega cisterna magna. Chromosomal analysis confirmed a normal female 46,XX karyotype and the array comparative genomic hybridization analysis revealed normal. Whole exome sequencing idientified a de novo heterozygous inframe deletion of c.3643_645del (p.Lys215del) in the HNRNPU gene, and she was diagnosed with HNRNPU-NDD. Conclusion: Speech delay, especially in the presence of other neurological findings such as microcephaly and intellectual disability, may be a clue to an underlying neurogenetic disease, and with the development of modern genetic diagnostic methods, the number of patients diagnosed is increasing day by day.

Mert Altıntaş
Ankara University Faculty of Medicine
Turkey

Miraç Yıldırım
Ankara University Faculty of Medicine
Turkey

Ömer Bektaş
Ankara University Faculty of Medicine
Turkey

Serap Teber
Ankara University Faculty of Medicine
Turkey