Table 1.
Clinical Characteristics
| Individual | 1 | 2 | 3 | 4 |
|---|---|---|---|---|
| Variant | Gly567Ser | Gly567Ser | Ile462Asn | Gly168Glu |
| Gender | male | male | female | male |
| Current age | 21Y | 18Y | 5Y | 4Y |
| Age at last assessment | 14Y | 17Y | 5Y | 4Y |
| Nystagmus | ||||
| Age at onset | 14D | 1D | 10 D | 1D |
| Age resolved | 5Y | 7Y | 12M | 14M |
| Development | ||||
| Walking without support | 20M | 17M | 26M | 36M |
| Language development | normal | slightly delayed | normal | delayed |
| MRI | ||||
| Myelin deficit (age) | 9.5M | 21D, 14M | 3M, 31M | 5M, 13M |
| Myelin normalization (age) | 12Y∗ | 8Y∗ | N/A | 4Y∗ |
| Myopia | + | + | − | + |
| Findings at last neurological examination | optic atrophy, mild ataxia | mild ataxia | unclear pronunciation | bilateral Babinski sign, unclear pronunciation |
| Other | Crohn disease, one self-limiting episode of vertigo | patent ductus arteriosus, hypospadia, abnormal BAEP and VEP | none | abnormal BAEP and VEP |
| Additional clinically relevant genetic findings | none | none | none | GRIA1 (NM_001258022.1c.1) c.936G>A (p.Ala646Thr); inheritance: de novo |
Abbreviations: Y, years; D, days; M, months; N/A, not available; ∗, earliest exam available; BAEP, brain-stem auditory evoked potential; VEP, visual evoked potential.