| Domain | Phenotype (plain) | Suggested HPO term(s) | Frequency/quantitative data | Typical onset/course | Key notes | Key sources (citation ids) |
|---|---|---|---|---|---|---|
| Neurodevelopment | Global developmental delay / psychomotor delay | HP:0001263 Developmental delay; HP:0001270 Motor delay | Reported as universal in classic BFPP series; mental retardation and motor developmental delay in 100% of 29 typical BFPP cases | Congenital/infantile onset; chronic, nonprogressive structural brain disorder with lifelong impairment | Core defining clinical feature across cohorts | (pqac-00000001, pqac-00000011, pqac-00000009) |
| Cognition | Intellectual disability / severe cognitive impairment | HP:0001249 Intellectual disability; HP:0011342 Severe global developmental delay | Severe cognitive impairment in 79.3% of reviewed cases | Apparent in infancy/early childhood; persistent | Often accompanied by markedly limited language acquisition | (pqac-00000002, pqac-00000013) |
| Epilepsy | Seizures / epilepsy | HP:0001250 Seizure; HP:0002373 Febrile seizures; HP:0002123 Generalized myoclonic seizure; HP:0002121 Absence seizure | 95% in 29-patient classic BFPP cohort; 88.2% (60/68) in review; refractory in 60.0% (36/60) of those with seizures; 90.4% (75/83) in 2024 review with refractory seizures in 54.7% (41/75) | Usually infancy to childhood onset; often chronic and can be drug-refractory | Lennox-Gastaut phenotype reported in some families; seizure types include atonic, atypical absence, myoclonic, tonic, spasms | (pqac-00000001, pqac-00000004, pqac-00000005, pqac-00000006, pqac-00000015) |
| Cerebellar / coordination | Cerebellar signs / ataxia | HP:0001251 Ataxia; HP:0002070 Cerebellar atrophy (imaging adjunct) | 94% in classic BFPP cohort; 92.6% in later literature review | Early childhood; generally persistent/nonprogressive relative to malformation | Reflects characteristic cerebellar involvement on MRI and exam | (pqac-00000001, pqac-00000013, pqac-00000009) |
| Eye movement | Dysconjugate gaze / oculomotor abnormalities | HP:0000608 Abnormality of the eye movement; HP:0000486 Strabismus; HP:0000511 Nystagmus | Dysconjugate gaze in 88% of classic BFPP cohort; oculomotor abnormalities in 92.1% in later review; strabismus 59.5% among those with oculomotor findings | Usually recognized in infancy/childhood; persistent | Commonly includes strabismus and nystagmus | (pqac-00000001, pqac-00000002, pqac-00000013, pqac-00000012) |
| Motor / pyramidal | Pyramidal signs / spasticity / brisk reflexes | HP:0002493 Upper motor neuron dysfunction; HP:0001257 Spasticity; HP:0001347 Hyperreflexia; HP:0002509 Limb hypertonia | Pyramidal signs present in 75.9% in review | Infantile/childhood onset; chronic | Can include spastic quadriparesis, ankle clonus, wide-based gait, hyperreflexia | (pqac-00000002, pqac-00000006, pqac-00000013) |
| Motor function | Ambulation outcome | HP:0002505 Impaired ambulation; HP:0002540 Delayed walking | Able to walk in 81.6% overall in 2021 review; median walking age 3.5 years; unable to walk 18.4%; 44/63 (~70%) able to walk in 2024 review | Delayed acquisition in childhood; variable ultimate attainment | Walking ability is variable and useful for severity stratification | (pqac-00000002, pqac-00000003, pqac-00000010) |
| Tone / early presentation | Hypotonia, sometimes evolving to hypertonia | HP:0001252 Hypotonia; HP:0001276 Hypertonia | No pooled percentage available in cited excerpts | Often first year of life or noted at birth; chronic | Early pseudomyopathic presentation can mimic congenital muscular dystrophy | (pqac-00000003, pqac-00000014, pqac-00000012) |
| Growth / head size | Head circumference usually normal; occasional microcephaly or macrocephaly | HP:0000252 Microcephaly; HP:0000256 Macrocephaly | Normal head circumference 85.1% in 2021 review; 81% in 2024 review; microcephaly 12.7%, macrocephaly 6.3% in 2024 review | Congenital/childhood trait; generally stable descriptor | Head size is not usually markedly abnormal despite severe neurologic disease | (pqac-00000004, pqac-00000015) |
| Imaging / cortex | Bilateral frontoparietal polymicrogyria with anterior-posterior gradient | HP:0002126 Polymicrogyria; HP:0012650 Bilateral cerebral cortical dysgenesis | Hallmark MRI pattern in essentially all classic BFPP cases; all 29 classic cases had bilateral frontoparietal PMG | Congenital, static malformation | Symmetric bilateral PMG with decreasing anterior-to-posterior severity is the canonical radiologic signature | (pqac-00000001, pqac-00000009, pqac-00000034) |
| Imaging / white matter | Patchy white-matter signal abnormalities / hypomyelination / reduced volume | HP:0002500 Abnormal cerebral white matter morphology; HP:0002188 Delayed CNS myelination | Present in all 29 classic cases as hallmark MRI finding; later reports describe diffuse hypomyelination in atypical severe cases | Congenital/static on serial imaging | May be patchy in classic BFPP or diffuse in atypical ADGRG1-related phenotypes | (pqac-00000001, pqac-00000003, pqac-00000034) |
| Imaging / posterior fossa | Brainstem and cerebellar hypoplasia | HP:0001321 Cerebellar hypoplasia; HP:0007366 Small pons | Present in all 29 classic cases as hallmark MRI finding | Congenital/static | Strong clue favoring ADGRG1-related BFPP over some other PMG subtypes | (pqac-00000001, pqac-00000007, pqac-00000034) |
| Severity / variability | Intrafamilial and interfamilial phenotypic variability | HP:0003812 Variable expressivity | Qualitative; no single pooled percentage | Lifelong, variable severity | Atypical diffuse polymicrogyria, pachygyria/lissencephaly-like changes, and severe non-ambulatory phenotypes have been reported | (pqac-00000002, pqac-00000010, pqac-00000012, pqac-00000016) |


*Table: This table summarizes the core clinical and imaging phenotype spectrum reported for ADGRG1-related bilateral frontoparietal polymicrogyria, with frequencies drawn from classic and updated literature reviews. It is useful for knowledge-base curation because it aligns phenotype terms, quantitative prevalence, and suggested HPO mappings with supporting citations.*