| Feature | Type (symptom/sign/lab/imaging) | Suggested HPO term | Evidence summary with numbers | Source (URL, year) |
|---|---|---|---|---|
| Encephalopathy / Altered consciousness | Symptom/Sign | HP:0002243, HP:0004372 | Requisite for pediatric ADEM per IPMSSG (not explained by fever); includes irritability, lethargy, or coma. Reported as the most frequent presenting feature (18.5% to >50% depending on cohort). (pqac-00000002, pqac-00000004, pqac-00000009) | Krupp et al., 2013 (https://doi.org/10.1177/1352458513484547); Mukhtiar et al., 2024 (https://doi.org/10.12669/pjms.40.7.8015) |
| Pyramidal signs / Motor deficit | Sign | HP:0002493, HP:0003470 | Observed in 68.7% of adult ADEM cases; 53.5% of pediatric cases in a single-center cohort. Often presents as polyfocal weakness or paresis. (pqac-00000004, pqac-00000044) | Li et al., 2022 (https://doi.org/10.3389/fimmu.2022.870867); Mukhtiar et al., 2024 (https://doi.org/10.12669/pjms.40.7.8015) |
| Fever and Headache | Symptom | HP:0001945, HP:0002315 | Very common prodromal and presenting features; typically lasting 3-4 days before progressing to encephalopathy. (pqac-00000004) | Mukhtiar et al., 2024 (https://doi.org/10.12669/pjms.40.7.8015) |
| Seizures | Sign | HP:0001250 | Reported in ~9.2% of post-vaccine cases; observed at a significantly lower frequency in MOG-seropositive pediatric ADEM compared to MOG-seronegative cases. (pqac-00000002, pqac-00000040) | Nabizadeh et al., 2023 (https://doi.org/10.1016/j.jocn.2023.03.008); Dong et al., 2023 (https://doi.org/10.3389/fnins.2023.1128422) |
| Large, diffuse white matter lesions | Imaging | HP:0002500, HP:0011036 | Abnormal brain MRI in 91.6% of adults (87.1% show white matter lesions). Lesions are typically bilateral, asymmetrical, poorly demarcated, >1-2 cm, and hyperintense on T2/FLAIR. T1 hypointensity is rare (unlike in MS). (pqac-00000009, pqac-00000024, pqac-00000046) | Krupp et al., 2013 (https://doi.org/10.1177/1352458513484547); Li et al., 2022 (https://doi.org/10.3389/fimmu.2022.870867) |
| Deep gray matter involvement | Imaging | HP:0012750 | Frequent involvement of the thalamus and basal ganglia; the corpus callosum is typically spared and Dawson fingers are absent (helpful to differentiate from MS). (pqac-00000009, pqac-00000024) | Krupp et al., 2013 (https://doi.org/10.1177/1352458513484547); Stoian et al., 2023 (https://doi.org/10.3390/vaccines11071225) |
| CSF pleocytosis and elevated protein | Lab | HP:0002128, HP:0002922 | Abnormal CSF found in 46.6% to 80% of cases. In adults, pleocytosis occurs in 51.8% and elevated protein in 39.1%. (pqac-00000004, pqac-00000046, pqac-00000049) | Li et al., 2022 (https://doi.org/10.3389/fimmu.2022.870867); Mukhtiar et al., 2024 (https://doi.org/10.12669/pjms.40.7.8015) |
| Oligoclonal bands (OCB) absence | Lab | HP:0003261 | OCB positivity is low in ADEM (~20% to 23.9% in adults) compared to MS (>80%), serving as a key diagnostic differentiator. (pqac-00000011, pqac-00000046) | Li et al., 2022 (https://doi.org/10.3389/fimmu.2022.870867) |
| MOG-IgG Seropositivity | Lab | N/A | Detectable in >50% of pediatric ADEM cases; strongly associated with multiphasic disease and higher relapse risk, though onset disability is often milder. (pqac-00000007, pqac-00000040) | Dong et al., 2023 (https://doi.org/10.3389/fnins.2023.1128422) |


*Table: A summary of the core clinical symptoms, imaging findings, and laboratory test results characteristic of ADEM, including differences from MS and corresponding HPO terms.*