| Phenotype (plain language) | Suggested HPO term (name; HP:ID if known) | Frequency/statistics | Notes/citations |
|---|---|---:|---|
| Headache | Headache; HP:0002315 | 63.6% in a 44-patient CNS vasculitis cohort; 76.9% in biopsy-confirmed small-vessel PCNSV; in a 5-patient PCNSV series, 1 presented with headache and all reported progressive holocephalic headaches | Common presenting symptom across primary/secondary CNS vasculitis and small-vessel PCNSV; also highlighted as a predictor in PACNS vs ICAD analyses (pqac-00000002, pqac-00000003, pqac-00000014) |
| Altered cognition / encephalopathy / altered mental status | Encephalopathy; HP:0001298 | Altered cognition in 43.2% of 44-patient cohort; altered mental status in 61.5% of sv-PCNSV cohort; encephalopathy significantly associated with PACNS vs ICAD, OR 7.60 | Reflects diffuse CNS dysfunction and is repeatedly emphasized in PACNS presentations (pqac-00000002, pqac-00000003, pqac-00000014) |
| Focal weakness / unilateral weakness | Hemiparesis; HP:0001269 | Focal weakness in 38.6% of 44-patient cohort; unilateral weakness in 2/5 patients in one 2024 series | Typical focal neurologic deficit in PACNS presentations (pqac-00000002, pqac-00000003) |
| Seizures | Seizure; HP:0001250 | 1/5 patients in Sheikh 2024; PACNS patients had seizures more often than secondary CNS vasculitis in 2025 cohort (40% vs 5%); seizure strongly associated with PACNS vs ICAD, OR 23.00 | Recurrent expert signal for PACNS, especially tumor-like and inflammatory presentations (pqac-00000003, pqac-00000007, pqac-00000014) |
| Cognitive impairment | Cognitive impairment; HP:0100543 | Cognitive changes reported in all 5 patients in Sheikh 2024; cognitive or visual impairment in 2/5 on initial exam | Often accompanies headache/progressive symptoms and contributes to disability (pqac-00000003) |
| Gait abnormality | Abnormality of gait; HP:0001288 | 1/5 in Sheikh 2024 presented with cognitive and gait abnormality | Suggests subcortical or multifocal lesion burden (pqac-00000003) |
| Visual impairment | Visual impairment; HP:0000505 | 2/5 had cognitive or visual impairment on initial exam in Sheikh 2024 | May occur with focal deficits or posterior circulation/optic pathway involvement (pqac-00000003) |
| Stroke-like episodes / acute ischemic events | Stroke; HP:0001297 | 78.7% (11/14) in D’Aniello 2024 imaging cohort presented with stroke-like episodes | CNS vasculitis frequently presents as ischemic cerebrovascular syndrome (pqac-00000013) |
| Transient ischemic attack-like episodes | Transient ischemic attack | 7.1% (1/14) in D’Aniello 2024 imaging cohort | Less common than stroke-like presentation in retrieved evidence (pqac-00000013) |
| Hemorrhagic lesions / intracranial hemorrhage / microhemorrhages | Intracranial hemorrhage; HP:0002170 | SWI hemorrhages in 96.4% (54/56) of biopsy-proven PCNSV; MRI in Sheikh 2024 showed hemorrhage among abnormalities | Hemorrhagic burden, especially microhemorrhages on SWI, is a notable imaging-associated phenotype in biopsy-proven disease (pqac-00000011, pqac-00000003) |
| White matter lesions | Abnormal cerebral white matter morphology | Most MRI lesions in biopsy-proven PCNSV were bilateral diffuse discrete-to-confluent white matter lesions | Frequent radiologic phenotype; frontal lobe predominance reported (pqac-00000012, pqac-00000011) |
| Vasogenic edema | Cerebral edema; HP:0002185 | Reported among MRI abnormalities in Sheikh 2024; edema present in 87% of tumor-like PACNS cases reviewed in 2025 systematic review | Important radiologic manifestation that can mimic tumor/inflammatory lesions (pqac-00000003) |
| Restricted diffusion / acute ischemic injury | Abnormality of brain imaging | DWI abnormalities corresponded to vessel-wall enhancement in 77% of CNS vasculitis patients on VW-MRI study | Suggests active ischemic injury in territories of inflamed vessels (pqac-00000010) |
| Contrast-enhancing brain lesions | Abnormal CNS imaging with contrast enhancement | Parenchymal enhancement in 96.3% (52/54) of biopsy-proven PCNSV; dot-linear pattern 87%, nodular 61.1%, perivascular 25.9%, patchy 16.7% | Strongly supportive MRI pattern in biopsy-proven disease, though not disease-specific (pqac-00000011) |
| Pseudotumoral / tumor-like mass lesions | Abnormality of CNS imaging | 45% of PACNS vs 10% of secondary CNS vasculitis in 2025 cohort; tumor-like PACNS recognized as a rare subtype in 2024 review | Important mimic of glioma/lymphoma; often requires biopsy for diagnosis (pqac-00000007) |
| Spinal cord involvement | Abnormality of the spinal cord | 15.8% in non-ABRA sv-PCNSV; spinal MRI involvement in 38.3% (12/33) in biopsy-proven PCNSV imaging series | Indicates disease is not always confined to brain parenchyma alone (pqac-00000011) |
| CSF pleocytosis | Cerebrospinal fluid pleocytosis; HP:0003565 | In PACNS vs ICAD, each +1 CSF WBC/µL increased odds of PACNS by 47% (OR 1.47, 95% CI 1.04–2.07); however, 17.4% of sv-PCNSV patients had normal CSF | CSF inflammation supports diagnosis but normal CSF does not exclude disease (pqac-00000014, pqac-00000008) |
| Low CSF glucose | Decreased cerebrospinal fluid glucose concentration | More common in secondary CNS vasculitis: 41.2% vs 8.7% in primary disease | Helps suggest secondary, especially infectious, etiologies rather than PACNS (pqac-00000002) |
| CSF oligoclonal bands | Oligoclonal bands in CSF | 63.6% in secondary CNS vasculitis vs 0 in primary disease in Hoshina 2024 | May help differentiate secondary CNS vasculitis from PACNS in the right context (pqac-00000002) |
| Fever / systemic inflammatory symptoms | Fever; HP:0001945 | 26.3% in secondary CNS vasculitis vs 0% in primary CNS vasculitis | Systemic features are uncommon in PACNS and may point toward secondary causes (pqac-00000002, pqac-00000003) |
| Need for walking aid / ambulatory disability | Gait disturbance / impaired mobility | In Sheikh 2024, all but one patient required walking aids initially; after treatment, 2 still required ambulatory aids | Illustrates quality-of-life and disability burden from neurologic deficits (pqac-00000003) |


*Table: This table summarizes reported clinical phenotypes and suggested HPO mappings for CNS vasculitis/PACNS, emphasizing frequencies and distinguishing features from recent cohorts and imaging studies. It is useful for knowledge-base phenotype annotation and for separating primary from secondary CNS vasculitis.*