*Correspondence: olavoleitemacedo@gmail.com.
Abstract
Case Presentation: A male patient at five months of age was taken to a pediatric neurology clinic with
a presentation of delayed psychomotor development and mild muscle spasms accompanied
by binocular supraversion for two months, occurring frequently at five times per day
with an average duration of one minute per episode, triggered when the patient became
irritated or cried. Additionally, the child presented significant axial hypotonia,
low nasal bridge, epicanthic folds, low-set ears, protuberant heels, and a gaze that
did not follow or fixate on eye contact. Neurological examination demonstrated head
control acquisition, tetraparesis with hypotonia, grade II symmetric reflexes, indifferent
bilateral plantar cutaneous reflex, and intact cranial nerves with isocoric, photoreactive
pupils and preserved extraocular motility, including occasional divergent strabismus.
A cranial magnetic resonance imaging revealed no structural brain abnormalities or
abnormal myelination. An electroencephalogram detected frequent interictal epileptiform
activity in the left centro-parieto-temporal region with rare multifocal abnormalities,
diffuse slowing of low amplitude, and asymmetry of the baseline activity. Comparative
genomic hybridization array was used to identify possible chromosomal alterations
causing infantile epileptic encephalopathy, showing a paternally inherited 170kb duplication
in band 3p25.2 on the short arm of chromosome 3 and another in region 10q26.3, which
did not fully explain the patient's phenotype. Whole-exome sequencing detected a GRIN2B
gene alteration with the variant Chr 12:13,720,098 promoting the substitution of glycine
for valine at codon 820 (p.Gly820Val), which was not inherited from the parents, indicating
a mutational event.
Discussion: The GRIN2B gene, located on the short arm of chromosome 12 at 12p13.1, encodes the
GluN2B subunit of the N-methyl-D-aspartate receptor, generating neural excitations.
Whole-exome sequencing allowed the detection of an extensive number of variants in
the GRIN2B gene, which have direct implications in various neurodevelopmental disorders
such as intellectual disability, autism spectrum disorder, visual impairment, and
infantile epileptic encephalopathy.
Final Comments: The importance of investigating genetic mutations using available tests in the field
must be underscored as a possible cause of epileptic syndromes, aiming to provide
therapeutic support to patients and improve their quality of life.
