Penetrance

Penetrance of GRIN2D-related DEE is thought to be 100%.

Source: GeneReviews — "GRIN2D-Related Developmental and Epileptic Encephalopathy"

Diagnostic Criteria

No consensus clinical diagnostic criteria for GRIN2D-related developmental and epileptic encephalopathy (GRIN2D-related DEE) have been published.

Suggestive Findings

GRIN2D-related DEE should be considered in individuals with the following clinical and/or brain MRI findings.

Clinical findings

• Mild-to-profound developmental delay (DD) or intellectual disability (ID); AND

• Any of the following presenting in infancy or childhood:

• Epilepsy

• Muscular tone abnormalities such as hypotonia and spasticity

• Dystonic, dyskinetic, or choreiform movement disorder

• Autism spectrum disorder

• Cortical visual impairment

Imaging findings. Brain MRI can show generalized volume loss as a sign of cerebral atrophy.

Establishing the Diagnosis

The diagnosis of GRIN2D-related DEE is established in a proband with suggestive fi...

Source: GeneReviews — "GRIN2D-Related Developmental and Epileptic Encephalopathy"

Differential Diagnosis

Because the phenotypic features associated with GRIN2D-related developmental and epileptic encephalopathy (GRIN2D-related DEE) are not sufficient to diagnose this condition, all disorders with the following features should be considered in the differential diagnosis:

• Intellectual disability without other distinctive findings: see OMIM Autosomal Dominant,

Autosomal Recessive, Nonsyndromic X-Linked, and Syndromic X-linked Intellectual Developmental Disorder Phenotypic Series.

• Developmental and epileptic encephalopathy: see OMIM Developmental and Epileptic Encephalopathy Phenotypic Series.

Of note, malformation of cortical development – described in some individuals with GRIN1- or GRIN2B-related neurodevelopmental disorder – has not been observed in GRIN2D-related DEE.

Source: GeneReviews — "GRIN2D-Related Developmental and Epileptic Encephalopathy"

Management Guidelines

No clinical practice guidelines for GRIN2D-related DEE have been published. Evaluations Following Initial Diagnosis To establish the extent of disease and needs in an individual diagnosed with GRIN2D-related DEE, the evaluations summarized (if not performed as part of the evaluation that led to the diagnosis) are recommended. Table 2. Recommended Evaluations Following Initial Diagnosis in Individuals with GRIN2D-Related DEE

Source: GeneReviews — "GRIN2D-Related Developmental and Epileptic Encephalopathy"

Therapies Under Investigation

Given the understanding of the drug memantine on GRIN2D function , anti-convulsant effects in animal models , and safety profile in children , memantine was tried in three affected individuals. While one showed a beneficial response, two did not . Due to the varying success of treatment with memantine, a targeted treatment recommendation cannot be given at this point. Search ClinicalTrials.gov in the US and EU Clinical Trials Register in Europe for access to information on clinical studies for a wide range of diseases and conditions. Note: There may not be clinical trials for this disorder.

Source: GeneReviews — "GRIN2D-Related Developmental and Epileptic Encephalopathy"

Surveillance Guidelines

Table 4. Recommended Surveillance for Individuals with GRIN2D-Related DEE

Source: GeneReviews — "GRIN2D-Related Developmental and Epileptic Encephalopathy"