Table 1. Clinical data of the patients with a homozygous GRIN1 mutation from the present study and from Lemke et al. ⁵ .

	Present family		Family 1 [5]		Family 2 [5]
Variant	c.679G>C p.(Asp227His)	c.679G>C p.(Asp227His)	c.742C>T p.(Arg217Trp)	c.649C>T p.(Arg217Trp)	c.1666C>T p.(Gln556*)	c.1666C>T p.(Gln556*)	c.1666C>T p.(Gln556*)
Sex	F	M	M	M	M	F	F
Age at inclusion	5.5y	3y	13.5y	12y	† 5mo	† 12d	† 5d
Seizure onset	No seizures	No seizures	No seizures	No seizures	1st d	1st d	1st d
Seizure type at onset	None	None	None	None	Myoclonic, clonic with desaturation, continuous	Clonic, continuous	Clonic, continuous
Seizure outcome	None	None	None	None	Deceased from status epilepticus	Deceased due to ongoing seizures and desaturation	Deceased due to ongoing seizures
EEG at onset	Normal	ND	6 months of age: spikes during sleep	10 months: diffuse spikes and waves during sleep	Burst suppression	Burst suppression	Burst suppression
Development	Severe ID. No language or walking	Severe ID. No language or walking	Severe ID. No language or walking	Severe ID. No language or walking	No development until death	† 12d	† 5d
Behavior	Autistic, stereotypic movements of the midline.	Autistic, stereotypic movements of the midline	Autistic agitated, hyperventilation, outbursts of laughing, stereotypic movements of the midline. Self-injury	Autistic, stereotypic movements of the midline. Agitated	—	—	—
Neurological examination	Hypotonia	Hypotonia	Axial hypotonia, tetraspastic, distal amyotrophy, dystonic features of knees and ankles	Axial hypotonia, tetraspastic distal amyotrophy	Hypotonia at birth, later hypertonia	Hypertonia, opisthotonic posturing	No formal exam due to continuous convulsions
Vision	Normal ERG	ND	Macular atrophy at ERG with normal visually evoked potential		Unknown	Unknown	Unknown
Additional features	Frontal bossing, mild midface hypoplasia	Frontal bossing, left transverse palmar crease	Constipation	Constipation, gynecomastia, macroglossia, sleep disturbances	Hyperlaxity thumbs, gap between first and second toe	—	—
Brain MRI	Mild atrophy, thin corpus callosum (18 m)	Normal (1y)	Normal (at 6 m)	Normal (at 10 m)	1 s month: possible punctiform hemorrhage in thalami	TFE (no MRI): two small periventricular cysts	Post-mortem MRI: microcephaly, delayed formation of sulci and delayed myelinisation

Abbreviations: d, day; EEG, electro encephalogram; ERG, electroretinogram, F, female; ID, intellectual deficiency; M, male; mo, month; ND, not done; TFE, transfontanellar echography; y, years.The reference cDNA and protein sequences used for numbering are NM_007327.3 and NP_015566.1, respectively. ^†Age at death.